AJAX延时等待的显示

<span id=ad_03 ><img src="js/loading.gif"/></span>
<!--QQ-->
<SPAN class=spanclass id=span_ad_03 style="DISPLAY: none">
<SCRIPT src="js/qq.js"  type=text/javascript></SCRIPT>
</SPAN>

<SCRIPT>
setTimeout('ad_03.innerHTML=span_ad_03.innerHTML;span_ad_03.innerHTML=""',3000);<!--延时2秒显示->
</SCRIPT>