// convert all characters to lowercase to simplify testing 
    var agt=navigator.userAgent.toLowerCase(); 

    // *** BROWSER VERSION *** 
    // Note: On IE5, these return 4, so use is_ie5up to detect IE5. 
    var is_major = parseInt(navigator.appVersion); 
    var is_minor = parseFloat(navigator.appVersion); 

    // Note: Opera and WebTV spoof Navigator.  We do strict client detection. 
    // If you want to allow spoofing, take out the tests for opera and webtv. 
    var is_nav  = ((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1) 
                && (agt.indexOf('compatible') == -1) && (agt.indexOf('opera')==-1) 
                && (agt.indexOf('webtv')==-1)); 
    var is_nav2 = (is_nav && (is_major == 2)); 
    var is_nav3 = (is_nav && (is_major == 3)); 
    var is_nav4 = (is_nav && (is_major == 4)); 
    var is_nav4up = (is_nav && (is_major >= 4)); 
    var is_navonly      = (is_nav && ((agt.indexOf(";nav") != -1) || 
                          (agt.indexOf("; nav") != -1)) ); 
    var is_nav5 = (is_nav && (is_major == 5)); 
    var is_nav5up = (is_nav && (is_major >= 5)); 

    var is_ie   = (agt.indexOf("msie") != -1); 
    var is_ie3  = (is_ie && (is_major < 4)); 
    var is_ie4  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.0")==-1) ); 
    var is_ie4up  = (is_ie  && (is_major >= 4)); 
    var is_ie5  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.0")!=-1) ); 
    var is_ie5up  = (is_ie  && !is_ie3 && !is_ie4);