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){
	if(Id>0&&Id<=5){
		for(var i=1;i<=5;i++){
			GetObj("tab_"+i).style.display = "none";
		}
		GetObj("tab_"+Id).style.display = "block";
		GetObj("tab_t1").style.background = "url("+bgImg+")";
	}else if(Id>5&&Id<=9){
		for(var i=6;i<=9;i++){
			GetObj("tab_"+i).style.display = "none";
		}
		GetObj("tab_"+Id).style.display = "block";
		GetObj("tab_t2").style.background = "url("+bgImg+")";
	}else if(Id>9&&Id<=13){
		for(var i=10;i<=13;i++){
			GetObj("tab_"+i).style.display = "none";
		}
		GetObj("tab_"+Id).style.display = "block";
		GetObj("tab_t3").style.background = "url("+bgImg+")";
	}else if(Id>13&&Id<=17){
		for(var i=14;i<=17;i++){
			GetObj("tab_"+i).style.display = "none";
		}
		GetObj("tab_"+Id).style.display = "block";
		GetObj("tab_t4").style.background = "url("+bgImg+")";
	}
}