var sall,bgObj

function ShowBackground()
{
	
	sall=document.getElementsByTagName("select"); //--------------把所有select标签捉住
	for(var j=0;j<sall.length;j++){sall[j].style.visibility ="hidden";} //--------------设为不显示，再进行下面操作
	
	var titleheight = "22"; // 提示窗口标题高度 

	
	var iWidth = document.documentElement.clientWidth; 
	var iHeight = document.documentElement.clientHeight; 
	if(iHeight<1500)
		iHeight=1500;
		
		
		
		  bgObj = document.createElement("div"); 
	bgObj.style.cssText = "position:absolute;left:0px;top:0px;width:"+iWidth+"px;height:"+iHeight+"px;filter:Alpha(Opacity=30);opacity:0.3;background-color:#000000;z-index:101;";
	document.body.appendChild(bgObj); 
}

function HideBackground()
{
	
	if(typeof(s_popdiv)!="undefined")
	{
		return ;
	}
	
	for(var j=0;j<sall.length;j++){sall[j].style.visibility="visible";} //--------------再给select显出来
	
  document.body.removeChild(bgObj); 

}