// **** global vars ****
var isNav4, isIE4, isWin, isMac, isIE5_Mac, isGecko, isOpera;

// ****  select browser: ****
if (parseInt(navigator.appVersion.charAt(0)) >= 4) {
  var agt=navigator.userAgent.toLowerCase();
  isDOM = (document.getElementById) ? true: false; // check for DOM level 1 compliant browsers (IE5+, NS6+)
  isGecko = (agt.indexOf('gecko') != -1); // Netscape 6.x Gecko engine
  isNav4 = (navigator.appName == "Netscape" && !isDOM ) ? true : false;
  isWin = ( (agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1) );
  isMac = (agt.indexOf("mac")!=-1);
  isIE = (agt.indexOf("msie")>-1);
  isIE4 = (agt.indexOf("msie 4")>-1); // updated on 8/4/2002
  isIE5_Mac = (isMac && (agt.indexOf("msie 5")>-1));
  isIE4_Mac = (isMac && isIE4);
  
	// check for Opera
	// Opera can announce itself as either Opera, Netscape (several versions) and MSIE5 (= default) so care must be taken to do a double check 
    var isOpera = (agt.indexOf("opera") != -1);
    var isOpera2 = (agt.indexOf("opera 2") != -1 || agt.indexOf("opera/2") != -1);
    var isOpera3 = (agt.indexOf("opera 3") != -1 || agt.indexOf("opera/3") != -1);
    var isOpera4 = (agt.indexOf("opera 4") != -1 || agt.indexOf("opera/4") != -1);
    var isOpera5 = (agt.indexOf("opera 5") != -1 || agt.indexOf("opera/5") != -1);
	var isOpera6 = (agt.indexOf("opera 6") != -1 || agt.indexOf("opera/6") != -1);
    var isOpera5up = (isOpera && !isOpera2 && !isOpera3 && !isOpera4);
	
	//if (isOpera) alert ("You're using Opera : "+agt+" isDOM= "+isDOM); else alert(agt+" navigator.appName="+navigator.appName);  
 
} else {
	alert ("Please use a recent browser, version 5 or later");
	// ...should redirect to some download page...
}