ie6 兼容 fixed

#top{
position:fixed;
_position:absolute;
bottom:0;
right:20px;
_bottom:auto;
_top:expression(eval(document.documentElement.scrollTop+document.documentElement.clientHeight-this.offsetHeight-(parseInt(this.currentStyle.marginTop,10)||0)-(parseInt(this.currentStyle.marginBottom,10)||0)));

position:fixed; 闪动问题

*html{
background-image:url(about:blank);
background-attachment:fixed;
}