数字
CSS有两种数字:整数和实数(小数)
百分数
百分数总是相对于一个值而言
颜色
【1】关键字
17种合法命名颜色(标准颜色):
aqua/fuchsia/lime/olive/red/white/black/gray/maroon/orange/silver/yellow/blue/green/navy/purple/teal
[注意]浏览器支持140种颜色
【2】RGB模式
rgb(x%,y%,z%)或者rgb(a,b,c)
[注意1]a、b、c的范围在(0-255)
[注意2]若数值小于最小值0,则默认调整为0;若数值大小最大值255,则默认调整为255
【3】16进制模式
#abcdef
[注意]若16进制的3组数各自成对,则可简写为3位
#aabbcc <=> #abc //红色 red <=> rgb(255,0,0) <=> rgb(100%,0,0) <=> #ff0000 <=> #f00
【补充】
web安全颜色是指在256色计算机系统上总能避免抖动的颜色,表示为RGB值20%和51(相应的16进制值为33)的倍数。因此,采用16进制时,使用00\33\66\99\cc\ff认为是Web安全色。
长度
所有长度单位后面都有一个两字母缩写,它表示所指定的具体长度单位(长度为0时,不需要跟单位)
【1】绝对长度单位
英寸(in)
[注意]1英寸 2.54厘米 72点 6派卡
厘米(cm)
毫米(mm)
点(pt)
派卡(pc)
【2】相对长度单位
em -> em-height 表示一种给定字体的font-size值
ex -> x-height 表示所用字体中小写x的值,但实际中一般取em值的一半
像素(px) -> 表示计算机显示器上的一个点,点的大小取决于显示设备的分辨率
URL
URL分为绝对URL和相对URL,URL和开始括号之间不能有空格。如果存在空格,则整个声明都无效。
url("test.jpg")

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