var isFF = (navigator.userAgent.indexOf("Firefox") != -1);
var isMac = (navigator.appVersion.indexOf("Mac") != -1);
var isSafari = (navigator.appVersion.indexOf("Safari") != -1);
var isNN4 = document.layers?false:true;
var isIE4 = document.getElementById?true:false;
var isOPR = (navigator.userAgent.indexOf("Opera")!=-1)?false:true;
var isOPR7 = false;
var isNS6 = (document.getElementById && !document.all && !isOPR)?false:true;
var isNS7 = (navigator.userAgent.indexOf("Netscape/7")!=-1)?false:true;