// 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) && (agt.indexOf('hotjava')==-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_nav6 = (is_nav && (is_major == 5));
    var is_nav6up = (is_nav && (is_major >= 5));
    var is_gecko = (agt.indexOf('gecko') != -1);


    var is_ie     = ((agt.indexOf("msie") != -1) && (agt.indexOf("opera") == -1));
    var is_ie3    = (is_ie && (is_major < 4));
    var is_ie4    = (is_ie && (is_major == 4) && (agt.indexOf("msie 4")!=-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_ie5_5  = (is_ie && (is_major == 4) && (agt.indexOf("msie 5.5") !=-1));
    var is_ie5up  = (is_ie && !is_ie3 && !is_ie4);
    var is_ie5_5up =(is_ie && !is_ie3 && !is_ie4 && !is_ie5);
    var is_ie6    = (is_ie && (is_major == 4) && (agt.indexOf("msie 6.")!=-1) );
    var is_ie6up  = (is_ie && !is_ie3 && !is_ie4 && !is_ie5 && !is_ie5_5);

    // KNOWN BUG: On AOL4, returns false if IE3 is embedded browser
    // or if this is the first browser window opened.  Thus the
    // variables is_aol, is_aol3, and is_aol4 aren't 100% reliable.
    var is_aol   = (agt.indexOf("aol") != -1);
    var is_aol3  = (is_aol && is_ie3);
    var is_aol4  = (is_aol && is_ie4);
    var is_aol5  = (agt.indexOf("aol 5") != -1);
    var is_aol6  = (agt.indexOf("aol 6") != -1);

    var is_opera = (agt.indexOf("opera") != -1);
    var is_opera2 = (agt.indexOf("opera 2") != -1 || agt.indexOf("opera/2") != -1);
    var is_opera3 = (agt.indexOf("opera 3") != -1 || agt.indexOf("opera/3") != -1);
    var is_opera4 = (agt.indexOf("opera 4") != -1 || agt.indexOf("opera/4") != -1);
    var is_opera5 = (agt.indexOf("opera 5") != -1 || agt.indexOf("opera/5") != -1);
    var is_opera5up = (is_opera && !is_opera2 && !is_opera3 && !is_opera4);

    var is_webtv = (agt.indexOf("webtv") != -1); 

    var is_TVNavigator = ((agt.indexOf("navio") != -1) || (agt.indexOf("navio_aoltv") != -1)); 
    var is_AOLTV = is_TVNavigator;

    var is_hotjava = (agt.indexOf("hotjava") != -1);
    var is_hotjava3 = (is_hotjava && (is_major == 3));
    var is_hotjava3up = (is_hotjava && (is_major >= 3));
	
	
	
	
	
	// *** PLATFORM ***
    var is_win   = ( (agt.indexOf("win")!=-1) || (agt.indexOf("16bit")!=-1) );
    // NOTE: On Opera 3.0, the userAgent string includes "Windows 95/NT4" on all
    //        Win32, so you can't distinguish between Win95 and WinNT.
    var is_win95 = ((agt.indexOf("win95")!=-1) || (agt.indexOf("windows 95")!=-1));

    // is this a 16 bit compiled version?
    var is_win16 = ((agt.indexOf("win16")!=-1) || 
               (agt.indexOf("16bit")!=-1) || (agt.indexOf("windows 3.1")!=-1) || 
               (agt.indexOf("windows 16-bit")!=-1) );  

    var is_win31 = ((agt.indexOf("windows 3.1")!=-1) || (agt.indexOf("win16")!=-1) ||
                    (agt.indexOf("windows 16-bit")!=-1));

    var is_winme = ((agt.indexOf("win 9x 4.90")!=-1));
    var is_win2k = ((agt.indexOf("windows nt 5.0")!=-1));

    // NOTE: Reliable detection of Win98 may not be possible. It appears that:
    //       - On Nav 4.x and before you'll get plain "Windows" in userAgent.
    //       - On Mercury client, the 32-bit version will return "Win98", but
    //         the 16-bit version running on Win98 will still return "Win95".
    var is_win98 = ((agt.indexOf("win98")!=-1) || (agt.indexOf("windows 98")!=-1));
    var is_winnt = ((agt.indexOf("winnt")!=-1) || (agt.indexOf("windows nt")!=-1));
    var is_win32 = (is_win95 || is_winnt || is_win98 || 
                    ((is_major >= 4) && (navigator.platform == "Win32")) ||
                    (agt.indexOf("win32")!=-1) || (agt.indexOf("32bit")!=-1));

    var is_os2   = ((agt.indexOf("os/2")!=-1) || 
                    (navigator.appVersion.indexOf("OS/2")!=-1) ||   
                    (agt.indexOf("ibm-webexplorer")!=-1));

    var is_mac    = (agt.indexOf("mac")!=-1);
    // hack ie5 js version for mac
    if (is_mac && is_ie5up) is_js = 1.4;
    var is_mac68k = (is_mac && ((agt.indexOf("68k")!=-1) || 
                               (agt.indexOf("68000")!=-1)));
    var is_macppc = (is_mac && ((agt.indexOf("ppc")!=-1) || 
                                (agt.indexOf("powerpc")!=-1)));

	
	
	
	
// *** STYLESHEETS ***
					
	// Mac ones - NOT Netscape					
	if (is_mac) {
		document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
		}
		
			
	// PC ones - NOT Netscape	
	if (is_win) {
		document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
		}
					
	
	// Netscape stylesheets	
	if (is_nav3) {
			 document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
			}
			
	if (is_nav4) {
			 document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
			}	
			
	if (is_nav6up) {
			document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
			}
			
		
	// Opera & AOL
	if (is_opera) {
			 document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
			}
			
	if (is_aol) {
			 document.write('<link rel="stylesheet" href="../about_files/stylesheets/bt.css">')
			}