function checkBrowser()
	{
	crumbs = document.cookie.split("; ");
	for (i=0;i<crumbs.length;i++)
		{
		if (crumbs[i]=="tbBrowser=checked") {return}
		}
	ua = navigator.userAgent;
	validBrowser = true;
	switch (navigator.appName)
		{
		case "Netscape":
			mozVer = ua.substr("Mozilla/".length, 1);
			if (parseInt(mozVer)<5) {validBrowser = false; break;}
			nsPos = ua.indexOf("Netscape");
			if (nsPos!=-1)
				{
				nsVer = parseInt(ua.substr(nsPos+"Netscape/".length,1));
				if (nsVer<7) {validBrowser = false}
				}
			break;
		case "Microsoft Internet Explorer":
			aolPos = ua.indexOf("AOL");
			if (aolPos!=-1)
				{
				aolVer = parseInt(ua.substr(aolPos+"AOL ".length,1));
				if (aolVer<8) {validBrowser = false}
				}
			iePre = "MSIE ".length;
			iePos = ua.indexOf("MSIE");
			ieEnd = ua.indexOf(";", iePos);
			ieVer = parseFloat(ua.substr(iePos+iePre, ieEnd-iePos-iePre));
			switch (navigator.platform)
				{
				case "Win32":
					if (ieVer==5.5)
						{
						if (navigator.appMinorVersion.indexOf("SP2")==-1) {validBrowser = false; break;}
						}
					if (ieVer<6.0) {validBrowser = false}
					break;
				case "MacPPC":
					if (ieVer<5.2) {validBrowser = false}
					break;
				}
			break;
		}
	if (validBrowser==false) 
		{
		msg = "Your browser version does not meet our minimum technical requirements.\nPlease upgrade to a newer version or use an alternate web browser."
		msg += "\n\nTaxBrain minimum browser requirements:"
		msg += "\n\n\tMicrosoft Internet Explorer\n\t\t - Windows: v5.5 SP2 (v6.0 recommended)\n\t\t - Mac: v5.2"
		msg += "\n\tNetscape v7.x (or equivalent)"
		msg += "\n\tAOL 8.0"
		alert(msg)
		}
	document.cookie = "tbBrowser=checked";
	}