function GetObj(objName){
	if(document.getElementById){
		return eval('document.getElementById("' + objName + '")');
	}else if(document.layers){
		return eval("document.layers['" + objName +"']");
	}else{
		return eval('document.all.' + objName);
	}
}
function tab(Id,bgImg,bgImgh){
	if(Id>0&&Id<=3){
		for(var i=1;i<=3;i++){
			GetObj("tab_"+i).style.display = "none";
		GetObj("tab_t"+i).style.background = "url("+bgImgh+")";
		}
		GetObj("tab_"+Id).style.display = "block";
		GetObj("tab_t"+Id).style.background = "url("+bgImg+")";
	}
}