div实现遮罩

<div id="testHidden" align="center" style="display:none" >
<IMG id=waiting_img src="img/waiting.gif" align=middle border=0 />
正在处理，请稍等...
</div>

 

//产生遮罩
nstc.disableBodyArea = function(win){
if(!win){
win = window;
doc = document;
}else{
doc = win.document;
}
if(!doc.all) return false;//For firefox etc.
win.topCoverDiv=doc.createElement("<div style='z-index:100;position:absolute;top:expression(this.offsetParent.scrollTop);left:expression(this.offsetParent.scrollLeft);width:expression(document.body.offsetWidth);height:expression(document.body.offsetHeight);filter:alpha(opacity=20);background-color:#888888;' oncontextmenu='return false;'>");
win.topCoverDiv.innerHTML="&nbsp;"
doc.body.appendChild(topCoverDiv);

var allSelects=doc.getElementsByTagName("select");
for(var i=0;i<allSelects.length;i++) {
//allSelects[i].style.visibility="hidden";
allSelects[i].style.disabled=true;
allSelects[i].style.backgroundColor="#EEEEEE";
}
}

 

var testHidden=document.getElementById("testHidden");
testHidden.style.visibility="visible";
testHidden.style.display ="block";

 

以上代码便能产生遮罩，页面返回后，遮罩自动消失～～