js制作鼠标移动提示层

<script type="text/javascript">
function window.onload()
{
    var tip=document.createElement("DIV")
    tip.id="oTip"
    with(tip.style)
    {
        position="absolute"
        border="1px solid #363636"
        backgroundColor="#C0C0C0"
        font="normal 12px Tahoma"
        padding="1 3 1 3"
        display="none"
    }
    document.body.appendChild(tip)
    document.onmouseover=show
    document.onmouseout=hide
}
function show()
{
    if(event.srcElement.alt && event.srcElement.alt!="")
    {
        with(oTip.style)
        {
            posLeft=document.body.scrollLeft+event.x+10
            posTop=document.body.scrollTop+event.y+10
            oTip.innerText=event.srcElement.alt
            event.srcElement.alt=""
            display="block"
        }
    }
}
function hide()
{
    event.srcElement.alt=oTip.innerText
    oTip.innerText=""
    oTip.style.display="none"
}
</script>
<img src="http://www.google.com/intl/en_ALL/images/logo.gif" alt="图片上的提示">
<button alt="按钮上的提示">按钮</button>
<a alt="链接上的提示">链接</a>