var browserName = navigator.appName;
var browserVersion = parseInt(navigator.appVersion);

function remind (){
if ((browserName == "Netscape" && browserVersion >= 3) || (browserName == "Microsoft Internet Explorer" && browserVersion >= 4)) {} else {alert('You need Netscape 3.0 - 4.0 or Internet Explorer 4.0 to browse information on that page !');}
}