CSS属性书写顺序
遵循以下顺序
1: 布局定位属性:display/position/float/clear/visibility/overfolw
2: 自身属性: width/height/margin/padding/border/background
3: 文本属性: color/font/text-decoration/text-align/vertial-align/white-space/breack-word
4: 其他属性(CSS3): content/cursor/border-radius/box-shadow/text/shadow