???

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;   
      	 //以下进行测试   
    	if (Sys.ie) {alert("IE");};   
    	if (Sys.firefox) {alert("firefox");};   
    	if (Sys.chrome) {alert("chrome");};   
    	if (Sys.opera) {alert("opera");};   
    	if (Sys.safari) {alert("safari");};   

?