判断不同浏览器

    <script type="text/javascript">
         var Sys = {};
         var ua = navigator.userAgent.toLowerCase();
         if (window.ActiveXObject)
             Sys.ie = ua.match(/msie ([\d.]+)/)[1]
         else if (document.getBoxObjectFor)
             Sys.firefox = ua.match(/firefox\/([\d.]+)/)[1]
         else if (window.MessageEvent && !document.getBoxObjectFor)
             Sys.chrome = ua.match(/chrome\/([\d.]+)/)[1]
         else if (window.opera)
             Sys.opera = ua.match(/opera.([\d.]+)/)[1]
         else if (window.openDatabase)
             Sys.safari = ua.match(/version\/([\d.]+)/)[1];
        
        
         if(Sys.ie) document.write('IE: '+Sys.ie);
         if(Sys.firefox) document.write('Firefox: '+Sys.firefox);
         if(Sys.chrome) document.write('Chrome: '+Sys.chrome);
         if(Sys.opera) document.write('Opera: '+Sys.opera);
         if(Sys.safari) document.write('Safari: '+Sys.safari);


     </script>