// 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);                                        
      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_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);