css中的样式缩写 border/margin/background/font/list
border:1px solid #000;
background: #f00 url(background.gif) no-repeat fixed 0 0;
font:italic small-caps bold 1em/140% "lucida Grande",sans-serif;
list-style: square inside url(image.gif);
margin:20px 20px 5px 20px;(上右下左顺时针方式)