absolute fixed效果 复制网页打开就是代码 http://www.cnblogs.com/0banana0/archive/2011/05/25/2056643.html

<div style="position: fixed; top: 100px; left: 60px;  180px; background-color: red;">

This div is using a fixed position of 100 pixels from the top and 60 pixels from the left of its containing block. When this page scrolls, this box will remain in a fixed position - it won't scroll with the rest of the page. Go on - SCROLL!

</div>

This tall div is absolutely positioned 500 pixels from the top and 60 pixels from the left of its containing block.

This div is using a fixed position of 100 pixels from the top and 60 pixels from the left of its containing block. When this page scrolls, this box will remain in a fixed position - it won't scroll with the rest of the page. Go on - SCROLL!