var ie = window.navigator.userAgent.indexOf("MSIE") != -1; 
var _div = document.createElement("DIV"); 
with(_div.style){ 
position = "absolute"; 
zIndex = "100"; 
top = "0"; 
left = "0"; 
width = "100%"; 
height = (document.body.scrollHeight+50) + "px"; 
backgroundColor = "#24426c"; 
if(ie){ 
filter = "Alpha(Opacity=70)";//0完全透明 
}else{ 
MozOpacity = 0.7;//0.0完全透明 
} 
} 

function run_grey(){
	document.body.appendChild(_div); 	
}

setTimeout("run_grey()",500);