showPop

function G(id){return document.getElementById(id);}

var popLoaded=false;

function showPop(url){

		var objSha = G("shadowDiv");
		objSha.style.height = document.body.scrollHeight+"px";
		objSha.style.width= document.body.scrollWidth+"px";
		objSha.style.left = 0;
		objSha.style.top = 0;
		
		/*if(!popLoaded){
			
 			try{
 				G("ifr").src= url;
				popLoaded=true;
 			}catch(e)
 			{
 				try{
 					document.frames["ifr"].location = url;
 					popLoaded=true;
				}catch(e){
					popLoaded=false;
				}
 			}
		}*/


		if(!popLoaded){
 			try{
 				G("ifr").src= url;
 			}catch(e)
 			{
 				document.frames["ifr"].location = url;
 			}
		}

		var objPop = G("popDiv");
		var sClientWidth = document.body.clientWidth;
		var sClientHeight = document.body.clientHeight;
		var sScrollTop = document.body.scrollTop;
		var sleft = (document.body.clientWidth / 2) - 0;
		var iTop = -80 + (sClientHeight / 2 + sScrollTop) - 0;
		var sTop = iTop > 0 ? iTop : (sClientHeight / 2 + sScrollTop) - 225;
		if(sTop < 1) sTop="20px";
		if(sleft < 1) sleft="20px";
				
		if(screen.width < 801){

			objPop.style.left = "20px";
			objPop.style.top = "20px";	
			objPop.style.height = "350px";

		}else if(screen.width > 1024){

			objPop.style.left = "300px";
			objPop.style.top = "170px";
			objPop.style.height = "500px";

		}else{		
			
			objPop.style.left = "180px";
			objPop.style.top = "120px";
			objPop.style.height = "500px";
		}

		objSha.style.display = "";
		objPop.style.display = "";

}

function hidePop(){

		G("popDiv").style.display = "none";
		G("shadowDiv").style.display = "none";

		
}
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<div id="shadowDiv" style="display:none;100%;height:100%;position:absolute;top:0px;left:0px;background-color:#FFF;filter: alpha(opacity=50);opacity:0.4;z-index:65534;border:solid 0px blue"></div>

<div id="popDiv" style="border:2px solid #97ACD2;display:none;position:absolute;top:0px;left:0px;650px;height:500px;overflow-y:auto;z-index:65535;background-color:#fff;">
	<div id="popTitle" style="border-bottom:0px solid #ccc;height:25px;">
		<strong style="float:left;margin-left:15px;font-size:14px;margin-top:5px;">选择主题图片</strong><a href="###" onclick="hidePop()" id="dialogBoxClose" style="color:#999999;text-decoration:none;float:right;margin-right:15px;font-size:14px;margin-top:5px;">X 关闭</a>
		<div class="clear"></div>
	</div>
	<div>
		<iframe id="ifr" frameborder="0" style="100%;height:460px;" scrolling="no" src="about:blank"></iframe></div>
	</div>
</div>
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<a href="###" onclick="javascript:showPop('/n/popup_setpic.aspx')">点此处选择一张主题图片</a>