让FireFox支持 window.event 全局事件对象

	//For firefox window.event
    if(typeof(window.event) == "undefined")
	{
		var $EventGetter = function(){
			var c=$EventGetter.caller; 
			while(c.caller)c=c.caller; 
			var evt = c.arguments[0];
			evt.srcElement = evt.target;
			return evt;
		}
		
		__defineGetter__("event", $EventGetter);
	}

	if(typeof(window.event) == "undefined")
	{
		var $E = function(){var c=$E.caller; while(c.caller)c=c.caller; return c.arguments[0]};
		__defineGetter__("event", $E);
	}

<button onclick="test();">Test</button>