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Summary of some knowledge points about HTML and CSS

零下一度
零下一度Original
2017-06-25 09:39:551293browse

A complete page consists of three parts:

  • html: Hypertext Markup Language

    • Through semantic tags, Build the page "structure"

  • css: Cascading style sheet

    • is responsible for the page "style" and beautify the page

  • js: lightweight scripting language; interaction refers to two places (behavior)

    • The front-end itself The "animation effect" written on the page

    • "data interaction" in the front and backend
      The combination of structure, style, and behavior

How to introduce css

  1. Embedded; (embedded)

    <style>
        body{
            height:100%;
            background-color: red;
        }
    </style>
  2. Inline style

    <body style="height:100%; background: #333333">
  3. External link type (real development, all external links are used)

    <link rel="stylesheet" href="style.css?1.1.11"/>

css priority

  • Inline>Inline>External link

css common properties and styles

  • When the setting is wrong, in the chrome control There will be a yellow exclamation mark as a prompt

  • color: color value; there are three ways to express color
    Shortcut key: c+tab

    • In English: red

    • rgb(255,0,0)

    • #fff

  • ##font-size: font size

    • Shortcut key: fsz30->font -size:30px


      font:400 14px/28px "宋体";

    ##background: Add background
  • Picture default Is horizontal repetition and vertical repetition

  • Position:
    • Horizontal position: left center right
    • Vertical position: top center bottom
    Comprehensive writing method:
  • background: url("images/bg2.png") no-repeat left center red;

    • background-image:url("image address")
    • background-repeat:no-repeat ; /repeat-x;/repeat-y
    • background-position:0 0
    • ##background-color:red
    • Whether the font is slanted
  • font-style: italic slant/normal normal
    • Underline and strikethrough
  • text-decoration: line-through; strikethrough
  • ##text-decoration: none; remove underline

  • text-decoration: underline;Add underline

  • Selector in css:

1. Label selector: div p ul li dt dd em i u del strong b input label from table

  • ##Disadvantages: Only common operations can be performed, and individual operations cannot be performed

    • 2.class selector

  • 3.id:

  • .class name
  • , the same page can have countless same class names
    • #id name

      , the same page can only have one ID name; (ID names cannot be repeated)
    • In the real development process, class is used to set styles, and id is used to obtain elements

      <div class="div1 div2 div3" id="div1"></div>
    • 4. Descendant selector: div p (select all p elements of descendants under the div container)

  • 5. Child selector: div > p (select the son under the div container); compatible with IE7+

  • 6. Intersection selector: div.div1

  • 7. Union selector: div, p

  • 8. Wildcard *: represents all elements

  • 9. Order selector: compatible with IE8+

  • div > p:first-child

    • ##div > p:last-child
    • 10. The next sibling selector ul li+li{} is compatible with IE7+

    • ##commonly used browsers for development
  • chrome

IE7~11
  • firefox
  • CSS inheritance and cascading
  • All attributes starting with font can be inherited; line-height

color can be inherited
  • Those starting with text can also be inherited, such as text-align
  • css weight
  • !important weight is infinite; (use less, the better)

The weight of id is greater than the weight of class
  • css box model
  • css box model consists of 5 parts :

    Content width and height+padding+border+margin
    • Centering of single line text: height = line- height
    • Centering, padding and line-height of multi-line text
  • padding:
    • padding是内边距

    • padding的颜色和内容的颜色一致;background-color填充的是border以内的颜色

    • padding是复合值
      padding:30px; ->pl30; pt30;pr30;pb30
      padding:20px 30px; ->上下为20px 左右30px
      padding:10px 20px 30px; -> 上10px 左右20px 下30px
      padding:10px 20px 30px 10px; 上 右 下 左

      如果现设置padding:30px
      再设置padding-left:10px
      请问最后的值各是多少?
      左10px; 其他都是30px

  • margin:外边框

  • border:

    • border:1px solid #000;

    • border-width

    • border-style:solid(实体),dashed(虚线),dotted(点)

    • border-color

行内元素和块级元素

  • p标签虽然是文本标签,但是它可以当容器来使用,p标签内一定不能放div; p段落也是块元素,他独占一行

  • 文本元素:p span a i em u b strong img

  • 容器级:div li dt dd h级(不建议)

  • 除了p,所有的文本元素,都是行内元素

  • 所有容器级别的元素,都是块元素

  • 块和行内元素的相互转化

    • display:inline; //行内

    • display:inline-block;//行内块

    • display:block; //块

  • 关于定位:大部分情况,建议的是:父相子绝(父亲:相对定位,儿子:绝对定位)

  • 关于脱离文档流的方法

  • 浮动 float:left; float:right;

  • 绝对定位 position:absolute;

  • 固定定位 position:fixed;

  • 重点:1)父相子绝 2)行内元素一点脱离文档流,就可以设置宽高了;

  • 注意:行内元素,一旦脱离文档流,虽然能设置宽高,但是,如果不设置宽的话,会默认跟内容一样宽;而块级元素,如果不设置宽度的话,默认跟父级一样块,没有父级的话,默认跟屏幕一样宽

  • 清除浮动

    • 固定高度height:xxxpx;
      缺点:如果作为产品列表的容器展示,我们无法知道容器的具体高度

    • overflow:hidden

    • clear:both
      缺点:可以解决浮动引起的文档流错乱问题,但是上面浮动元素的父容器该没有高度还没有高度

    • 伪类清除浮动

      ul::after{
      display: block;
      height:0;
      content: '';
      clear: both;
      }
  1. 溢出隐藏

  2. 清除浮动
    缺点:如果父容器比较小,子容器比较大;父容器如果通过overflow:hidden来清除浮动的话,子容器就看不到了

  • 透明度处理

    • rgba() 背景透明,文字不透明;

    • opacity:0 背景透明,文字也透明;

      opacity:0.1;/*不兼容IE7浏览器*/
      filter:alpha(opacity=10);

    最基本的开发,首先必须创建的项目结构

    • images文件夹:放切好的图片

    • css文件夹:放置css文件:index.css

    • index.html文件

    关于继承

    • 宽度继承:如果没有父级,块元素的宽度默认跟可视区一样宽;如果有父级的情况下,默认跟父级宽度一样宽(宽度可以继承,但高度无法继承;)

    • font可以继承

    • color可以继承:当遇到a标签的时候, color无效;

    • line-height可以继承

    当文本超度固定宽度的处理方法:

    • 单行文本出超固定宽度出现省略号的写法:

      white-space:nowrap;
      overflow:hidden;
      text-overflow:ellipsis
    • 英文不折行的问题处理: word-wrap:break-word;

    • 出现滚动条的写法overflow-y:scroll;

    区分伪类和伪元素

    • 伪元素:用:和::都可以,现在建议用::

    • 伪类:给当前选择器添加动效,只能用:

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