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;   }}