function isIEBrowser(){     var Sys = {};     var ua = navigator.userAgent.toLowerCase();     var s;        (s = ua.match(/msie ([\d.]+)/)) ? Sys.ie = s[1] :        (s = ua.match(/firefox\/([\d.]+)/)) ? Sys.firefox = s[1] :        (s = ua.match(/chrome\/([\d.]+)/)) ? Sys.chrome = s[1] :        (s = ua.match(/opera.([\d.]+)/)) ? Sys.opera = s[1] :        (s = ua.match(/version\/([\d.]+).*safari/)) ? Sys.safari = s[1] : 0;     if(Sys.ie){         return true;     } else {         return false;     }     //if (Sys.firefox || Sys.chrome || Sys.opera || Sys.safari){
         //}}

如何调用？看下面，防不住firefox -。-!

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