按鼠標效果（http://hi.baidu.com/xuexiang516168/blog/item/01d36144afaebb3586947367.html）

<script type= "text/javascript">

function showm()

{

var
oment;

var id="ImageButton1";

oment=document.getElementById(id);

oment.src="text4/down.gif";

return false;

}

function
shown()

{

var oment;

var id="ImageButton1";

oment=document.getElementById(id);

oment.src="text4/1.jpg";

return false;

}

</script>

protected void
Page_Load(object sender, EventArgs
e)

{

ImageButton1.Attributes.Add("onmouseover", "return
showm();");

ImageButton1.Attributes.Add("onmouseout", "return
shown();");

}