function setdisplay(){
	var ua = navigator.userAgent.toLowerCase(); 
	var isIE5 = (ua.indexOf("msie 5.0") != -1);
	var ok =	document.getElementById("bg1")&&
				document.getElementById("bg2")&&
				document.getElementById("bg3")&&
				document.getElementById("bg4");
	if (ok && !isIE5){
		document.getElementById("bg1").style.visibility="visible";
		document.getElementById("bg2").style.visibility="visible";
		document.getElementById("bg3").style.visibility="visible";
		document.getElementById("bg4").style.visibility="visible";
	}
}