style.top style.left 在IE和FireFox的区别

在IE中可以直接用obj.style.top=100;但在FireFox中必须加上单位，变成obj.style.top=100+'px';
style.left同理。

浏览器的判断：window.navigator.userAgent.indexOf("IE") == -1 //非IE浏览器  FireFox,Chrome

FireFox没有onmouseover和onmouseout,onclick事件,他们的写法为：

if(window.navigator.userAgent.indexOf("IE") == -1) //FireFox
{
     link.addEventListener('mouseover', function(){a = false}, true);
     link.addEventListener("mouseout",function(){a = true},true)
}
else //IE
{
     link.attachEvent("onmouseover",function(){a = false});
     link.attachEvent("onmouseout",function(){a = true});
}