替代window.event.srcElement效果的可兼容性的函数

function getEvent() 
{ 
var i = 0; 
if(document.all){ 
return window.event; 
} 

func = getEvent.caller; 
while(func != null) 
{ 
var arg0 = func.arguments[0]; 
if(arg0) 
{ 
if(arg0.constructor == MouseEvent) 
{ 
return arg0; 
} 
} 
func = func.caller; 
} 
return null; 
}

function buttonOver(e) 
{ 
e = getEvent(); 
var obj = e.srcElement || e.target; 
if (obj.runtimeStyle){ 
obj.runtimeStyle.cssText = "background-color:#FFFFFF"; 
} 
else 
obj.style.background = "#FFFFFF"; 
}