A brief analysis of CSS position:absolute

1. Characteristics of absolute positioning

Absolute positioning has the same characteristics as floating, namely wrapping and destructiveness.

In terms of destructiveness, floating only destroys the height of the element and retains the width of the element; while the height and width of absolutely positioned elements are gone.

Please see the code below:

<span style="color: #008080;"> 1</span> <span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 2</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 3</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 4</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="utf-8"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 5</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>绝对定位的特征<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 6</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 7</span> <span style="background-color: #f5f5f5; color: #800000;">            .box1,.box2,.box3 </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 8</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> orange</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 9</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin-bottom</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 30px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">10</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">11</span> 
<span style="color: #008080;">12</span> <span style="background-color: #f5f5f5; color: #800000;">            .absolute </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">13</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">14</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">15</span> 
<span style="color: #008080;">16</span> <span style="background-color: #f5f5f5; color: #800000;">            .wraper </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">17</span> <span style="background-color: #f5f5f5; color: #ff0000;">                display</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">inline-block</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">18</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin-left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 300px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">19</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">20</span> 
<span style="color: #008080;">21</span> <span style="background-color: #f5f5f5; color: #800000;">            .float </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">22</span> <span style="background-color: #f5f5f5; color: #ff0000;">                float</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> left</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">23</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">24</span>             
<span style="color: #008080;">25</span> <span style="background-color: #f5f5f5; color: #800000;">            .box3 </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">26</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">27</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">28</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">29</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">30</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">31</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box1"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">32</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">33</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://pic1.win4000.com/wallpaper/c/537b28b60619b.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:240px;height:180px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">34</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>这是普通流中的两幅图像。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">35</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">36</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box2"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">37</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="absolute"</span><span style="color: #ff0000;"> src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">38</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://pic1.win4000.com/wallpaper/c/537b28b60619b.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:240px;height:180px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">39</span> 
<span style="color: #008080;">40</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="wraper"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">41</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="float"</span><span style="color: #ff0000;"> src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">42</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://pic1.win4000.com/wallpaper/c/537b28b60619b.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:240px;height:180px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">43</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">44</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>左图，将第一幅图像绝对定位，其完全脱离文档流，并且覆盖在第二幅图像之上；由此看出，绝对定位的破坏性不仅让元素没有了高度，甚至没有了宽度。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">45</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>右图，将第一幅图像左浮动，其虽然脱离了文档流，但是并没有覆盖在其他元素之上；浮动的破坏性仅仅破坏了元素的高度，而保留了元素的宽度。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">46</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">47</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box3"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">48</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">49</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://pic1.win4000.com/wallpaper/c/537b28b60619b.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:240px;height:180px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">50</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>将容器绝对定位，体现其包裹性。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">51</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">52</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">53</span> <span style="color: #0000ff;"></</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>

View Code

2. General rules for absolute positioning:

When an element is positioned absolutely, it is completely out of the document flow and positioned relative to its containing block.

An absolutely positioned containing block is its nearest positioned ancestor element.

If this ancestor element is a block-level element, the containing block is the padding boundary of the ancestor element, that is, the border.

If the ancestor element is an inline element, the containing block is the content boundary of the ancestor element, that is, the content area.

If there is no positioned ancestor element, the element's containing block is defined as the initial containing block.

Offset attributes: top, right, bottom, left.

If an absolutely positioned element does not set an offset attribute, although it is out of the document flow, its position will remain in place.

The offset attribute can be negative to position the element outside the containing block.

The code is here:

<span style="color: #008080;"> 1</span> <span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 2</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 3</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 4</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="utf-8"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 5</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>绝对定位的一般规则<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 6</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 7</span> <span style="background-color: #f5f5f5; color: #800000;">            body </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 8</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> #ccc</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 9</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">10</span> <span style="background-color: #f5f5f5; color: #800000;">            .container </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">11</span> <span style="background-color: #f5f5f5; color: #ff0000;">                width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">500px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">12</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> orange</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">13</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">20px auto 50px auto</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">14</span> <span style="background-color: #f5f5f5; color: #ff0000;">                padding</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">20px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">15</span> <span style="background-color: #f5f5f5; color: #ff0000;">                border</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">2px solid red</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">16</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">17</span> 
<span style="color: #008080;">18</span> <span style="background-color: #f5f5f5; color: #800000;">            .box2 img,.box3 img,
</span><span style="color: #008080;">19</span> <span style="background-color: #f5f5f5; color: #800000;">            .box4 img,.box5 img </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">20</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">21</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">22</span> 
<span style="color: #008080;">23</span> <span style="background-color: #f5f5f5; color: #800000;">            .box3 img,.box4 img </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">24</span> <span style="background-color: #f5f5f5; color: #ff0000;">                left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">25</span> <span style="background-color: #f5f5f5; color: #ff0000;">                bottom</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">26</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">27</span> 
<span style="color: #008080;">28</span> <span style="background-color: #f5f5f5; color: #800000;">            .box5 img </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">29</span> <span style="background-color: #f5f5f5; color: #ff0000;">                left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> -30px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">30</span> <span style="background-color: #f5f5f5; color: #ff0000;">                bottom</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> -50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">31</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">32</span> 
<span style="color: #008080;">33</span> <span style="background-color: #f5f5f5; color: #800000;">            .block </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">34</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position </span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">relative</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">35</span> <span style="background-color: #f5f5f5; color: #ff0000;">                height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 200px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">36</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">37</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">38</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">39</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">40</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="container"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">41</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box1"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">42</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>元素绝对定位时，会完全脱离文档流，并相对于其包含块定位。绝对定位的包含块，是其最近的已定位的祖先元素。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">43</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">44</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">ul</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">45</span>                     <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>如果这个祖先元素是块级元素，包含块则为该祖先元素的内边距边界，即边框。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">46</span>                     <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>如果这个祖先元素是行内元素，包含块则为该祖先元素的内容边界，即内容区。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">47</span>                     <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>如果没有已定位的祖先元素，元素的包含块定义为初始包含块（一个视窗大小的矩形）。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>      
<span style="color: #008080;">48</span>                 <span style="color: #0000ff;"></</span><span style="color: #800000;">ul</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">49</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭box1</span><span style="color: #008000;">--></span>
<span style="color: #008080;">50</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭container</span><span style="color: #008000;">--></span>
<span style="color: #008080;">51</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="container"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">52</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box2"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">53</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>不管有没有已经定位的祖先元素，只要没有偏移量，绝对定位之后，原地不动，脱离文档流。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">54</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>下面这个已经绝对定位的图像原地没动，但是已经脱离了文档流。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">55</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">56</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭box2</span><span style="color: #008000;">--></span>
<span style="color: #008080;">57</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭container</span><span style="color: #008000;">--></span>
<span style="color: #008080;">58</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="container"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">59</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box3"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">60</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>没有已经定位的祖先元素，有偏移量，绝对定位之后，以初始包含块（一个视窗大小的矩形）为基准进行偏移。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">61</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>当偏移量为left:0; buttom:0时，图像水平偏移到了初始包含块左下角（打开网页最开始的那一个视窗的左下角）。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">62</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">63</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭box3</span><span style="color: #008000;">--></span>
<span style="color: #008080;">64</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭container</span><span style="color: #008000;">--></span>
<span style="color: #008080;">65</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="container block"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">66</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box4"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">67</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>有已经定位的祖先元素，有偏移量，绝对定位之后，以已经定位的祖先元素为基准进行偏移。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">68</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>此处已经定位的祖先元素为这个图像的容器div元素，偏移量为left:0; bottom:0时，图像到了这个容器的左下角（以边框为界）。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">69</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">70</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭box4</span><span style="color: #008000;">--></span>
<span style="color: #008080;">71</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭container</span><span style="color: #008000;">--></span>
<span style="color: #008080;">72</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="container block"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">73</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box5"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">74</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>有已经定位的祖先元素，有偏移量，绝对定位之后，以已经定位的祖先元素为基准进行偏移。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">75</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>此处已经定位的祖先元素为这个图像的容器div元素，偏移量为left:-30px; bottom:-50px时，图像到了这个容器之外（以边框为界）。<span style="color: #0000ff;"></</span><span style="color: #800000;">p</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">76</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://a.hiphotos.baidu.com/zhidao/pic/item/72f082025aafa40fa38bfc55a964034f79f019ec.jpg"</span><span style="color: #ff0000;"> alt</span><span style="color: #0000ff;">="A picture"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:175px;height:100px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">77</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭box5</span><span style="color: #008000;">--></span>
<span style="color: #008080;">78</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span><span style="color: #008000;"><!--</span><span style="color: #008000;">关闭container</span><span style="color: #008000;">--></span>
<span style="color: #008080;">79</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>    
<span style="color: #008080;">80</span> <span style="color: #0000ff;"></</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>

View Code

3. Use margin to adjust the position of absolutely positioned elements

Absolutely positioned elements, in addition to being offset using top, right, bottom, and left, can also be positioned accurately through margin values, and are more adaptable.

Example:

<span style="color: #008080;"> 1</span> <span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 2</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 3</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 4</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="utf-8"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 5</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>用margin调整绝对定位元素的位置<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 6</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 7</span> <span style="background-color: #f5f5f5; color: #800000;">            .box1,.box2,.box3 </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 8</span> <span style="background-color: #f5f5f5; color: #ff0000;">                display</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> inline-block</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 9</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin-right</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 150px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">10</span> <span style="background-color: #f5f5f5; color: #ff0000;">                border</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">1px solid blue</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">11</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">12</span>     
<span style="color: #008080;">13</span> <span style="background-color: #f5f5f5; color: #800000;">            span </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">14</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> red</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">15</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">16</span>     
<span style="color: #008080;">17</span> <span style="background-color: #f5f5f5; color: #800000;">            .box2 span,.box3 span </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">18</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">19</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">20</span>     
<span style="color: #008080;">21</span> <span style="background-color: #f5f5f5; color: #800000;">            .meng </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">22</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin-left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> -3em</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">23</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">24</span>     
<span style="color: #008080;">25</span> <span style="background-color: #f5f5f5; color: #800000;">            .box4 </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">26</span> <span style="background-color: #f5f5f5; color: #ff0000;">                border</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">1px solid red</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">27</span> <span style="background-color: #f5f5f5; color: #ff0000;">                width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 500px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">28</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px auto 0 auto</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">29</span> <span style="background-color: #f5f5f5; color: #ff0000;">                padding</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;">20px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">30</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">31</span> 
<span style="color: #008080;">32</span> <span style="background-color: #f5f5f5; color: #800000;">            li </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;">33</span> <span style="background-color: #f5f5f5; color: #ff0000;">                margin-bottom</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 20px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;">34</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;">35</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">36</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">37</span>     <span style="color: #0000ff;"><</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">38</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box1"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">39</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>卡哇伊<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">40</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://imgsrc.baidu.com/forum/w%3D580/sign=0c101fe665380cd7e61ea2e59145ad14/f9a3492762d0f7032de1758a08fa513d2797c542.jpg"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:200px;height:300px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">41</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>萌萌哒<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">42</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">43</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box2"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">44</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>卡哇伊<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">45</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://imgsrc.baidu.com/forum/w%3D580/sign=0c101fe665380cd7e61ea2e59145ad14/f9a3492762d0f7032de1758a08fa513d2797c542.jpg"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:200px;height:300px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">46</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>萌萌哒<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">47</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>    
<span style="color: #008080;">48</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box3"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">49</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>卡哇伊<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">50</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">img </span><span style="color: #ff0000;">src</span><span style="color: #0000ff;">="http://imgsrc.baidu.com/forum/w%3D580/sign=0c101fe665380cd7e61ea2e59145ad14/f9a3492762d0f7032de1758a08fa513d2797c542.jpg"</span><span style="color: #ff0000;"> style</span><span style="color: #0000ff;">="width:200px;height:300px"</span> <span style="color: #0000ff;">/></span>
<span style="color: #008080;">51</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">span </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="meng"</span><span style="color: #0000ff;">></span>萌萌哒<span style="color: #0000ff;"></</span><span style="color: #800000;">span</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">52</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>    
<span style="color: #008080;">53</span>         <span style="color: #0000ff;"><</span><span style="color: #800000;">div </span><span style="color: #ff0000;">class</span><span style="color: #0000ff;">="box4"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">54</span>             <span style="color: #0000ff;"><</span><span style="color: #800000;">ol</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">55</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>第一幅图，最开始的样子。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">56</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>第二幅图，两个标签绝对定位，但是不指定任何偏移量。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">57</span>                 <span style="color: #0000ff;"><</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>第三幅图，用margin负值调整“萌萌哒”的位置，完成。<span style="color: #0000ff;"></</span><span style="color: #800000;">li</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">58</span>             <span style="color: #0000ff;"></</span><span style="color: #800000;">ol</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">59</span>         <span style="color: #0000ff;"></</span><span style="color: #800000;">div</span><span style="color: #0000ff;">></span>        
<span style="color: #008080;">60</span>     <span style="color: #0000ff;"></</span><span style="color: #800000;">body</span><span style="color: #0000ff;">></span>
<span style="color: #008080;">61</span> <span style="color: #0000ff;"></</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>

View Code

Give up the offset attribute and use margin instead to adjust absolutely positioned elements. The principle is:

Absolutely positioned elements, when the offset is not set, although it is completely out of the document flow, it is still in its original position.

Use the offset attribute for precise positioning. The specific position depends on the containing block of the absolutely positioned element. Different containing blocks will have completely different positioning results.

Using margin for precise positioning does not depend on anything else and is more controllable.

While writing this blog post, absolute asked me to send a message to relative. It said: "relative, please get out of here, I don’t want to see you in this life! "

To predict what will happen next, please move to the relative chapter, click here!

4. Absolute positioning and overall layout

How to use absolute positioning to layout the page as a whole?

Simple and crude, it will be wasted if you don’t learn! ! !

<span style="color: #008080;"> 1</span> <span style="color: #0000ff;"><!</span><span style="color: #ff00ff;">DOCTYPE html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 2</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">html</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 3</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">head</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 4</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">meta </span><span style="color: #ff0000;">charset</span><span style="color: #0000ff;">="utf-8"</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 5</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>Absolute positioning and overall page layout<span style="color: #0000ff;"></</span><span style="color: #800000;">title</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 6</span> <span style="color: #0000ff;"><</span><span style="color: #800000;">style</span><span style="color: #0000ff;">></span>
<span style="color: #008080;"> 7</span> <span style="background-color: #f5f5f5; color: #800000;"> * </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 8</span> <span style="background-color: #f5f5f5; color: #ff0000;"> margin</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 9</span> <span style="background-color: #f5f5f5; color: #000000;">}</span><span style="background-color: #f5f5f5; color: #008000;">/*</span><span style="background-color: #f5f5f5; color: #008000;">Reset all margins to 0. This step is extremely important, otherwise the layout will be messed up.</span><span style="background-color: #f5f5f5; color: #008000;">*/</span>
<span style="color: #008080;"> 10</span> 
<span style="color: #008080;"> 11</span> <span style="background-color: #f5f5f5; color: #800000;">            html,body,.page </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 12</span> <span style="background-color: #f5f5f5; color: #ff0000;">                width</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 100%</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 13</span> <span style="background-color: #f5f5f5; color: #ff0000;">                height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 100%</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 14</span> <span style="background-color: #f5f5f5; color: #ff0000;">                overflow</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> hidden</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 15</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;"> 16</span> 
<span style="color: #008080;"> 17</span> <span style="background-color: #f5f5f5; color: #800000;">            .page </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 18</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 19</span> <span style="background-color: #f5f5f5; color: #ff0000;">                top</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 20</span> <span style="background-color: #f5f5f5; color: #ff0000;">                right</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 21</span> <span style="background-color: #f5f5f5; color: #ff0000;">                bottom</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 22</span> <span style="background-color: #f5f5f5; color: #ff0000;">                left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 23</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> #ccc</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 24</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;"> 25</span> 
<span style="color: #008080;"> 26</span> <span style="background-color: #f5f5f5; color: #800000;">            .header </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 27</span> <span style="background-color: #f5f5f5; color: #ff0000;">                position</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> absolute</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 28</span> <span style="background-color: #f5f5f5; color: #ff0000;">                height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 29</span> <span style="background-color: #f5f5f5; color: #ff0000;">                left</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 30</span> <span style="background-color: #f5f5f5; color: #ff0000;">                right</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 31</span> <span style="background-color: #f5f5f5; color: #ff0000;">                background-color</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> purple</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 32</span> <span style="background-color: #f5f5f5; color: #ff0000;">                padding</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 0 5px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 33</span> <span style="background-color: #f5f5f5; color: #ff0000;">                z-index</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 1</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 34</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>
<span style="color: #008080;"> 35</span> 
<span style="color: #008080;"> 36</span> <span style="background-color: #f5f5f5; color: #800000;">            .header>h1 </span><span style="background-color: #f5f5f5; color: #000000;">{</span>
<span style="color: #008080;"> 37</span> <span style="background-color: #f5f5f5; color: #ff0000;">                line-height</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> 50px</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 38</span> <span style="background-color: #f5f5f5; color: #ff0000;">                text-align</span><span style="background-color: #f5f5f5; color: #000000;">:</span><span style="background-color: #f5f5f5; color: #0000ff;"> center</span><span style="background-color: #f5f5f5; color: #000000;">;</span>
<span style="color: #008080;"> 39</span>             <span style="background-color: #f5f5f5; color: #000000;">}</span>