Hi ,
you can call java script function __doPostback(); if you use 'img' control
Script for Make PostBack :-
<script language="javascript">
<!--
function __doPostBack(eventTarget, eventArgument) {
var theform = document.ctrl2
theform.__EVENTTARGET.value = eventTarget
theform.__EVENTARGUMENT.value = eventArgument
theform.submit()
}
</script>
HTML Script
<a href="javascript:__doPostBack('imgPic','')" id="hrf1" >
<img id="imgPic" alt="" src="" />
</a>
I hope this solution Help you