browserName = navigator.appName;
		browserVer = parseInt(navigator.appVersion);

		ns3up = (browserName == "Netscape" && browserVer >= 3);
		ie4up = (browserName.indexOf("Microsoft") >= 0 && browserVer >= 4);

		function doPic(imgName) {
		if (ns3up || ie4up) {
		imgOn = ("" + imgName);
		document.mainpic.src = imgOn;
		}
		}