AOKWORLD

Step 1: Inset background:fixed in body.
Step 2: Use expression(offsetParent.scrollTop+offsetParent.clientHeight-400+'px');

body { background:url(imgs/pageBg.png) fixed;}
#menubar {
   	width:100px;
	height:100px;
	position:fixed;
	bottom:0;
	right:0;
	z-index:10000;
	_position:absolute;
	_top:expression(offsetParent.scrollTop+offsetParent.clientHeight-400+'px');
}

[if IE 6] example:

	html{overflow:hidden;}
	body{height:100%;overflow:auto;}
	#fixed{position:absolute;right:17px;}
	/* fixed元素的绝对位置是相对于HTML元素来说，而滚动条是body元素的，这是设置right:17px的原因 */
	#fixed { position:absolute; top:expression(eval(document.body.scrollTop + 50));}

You can:

/* IE7+ FF Other Standard Browser */
html > body #menubar {...}

/* IE6 Only */
* html  #menubar {...}