[Dim@]

<a id="ss">Ссылка</a>
<script type="text/javascript">
var ss = document.getElementById("ss");
ss.onmouseover = function (){
 if (ss.style) ss.style.opacity = ((ss.style.opacity == 0) ? 1 : 0);
 ss.time = setTimeout(arguments.callee, 100);
}
ss.onmouseout = function () {
 this.style.opacity = 0;
 clearInterval(this.time);
}
</script>