<script type="text/javascript">     
$('a.threadAuthorLink').hover(function (e) {
     e = e || window.event;
     $('body').append($('<div class="ava" style="background: #eee; border: 1px dashed black; position: absolute; width: 100px; height: 100px;"></div>').css({
      top: e.pageY,
      left: e.pageX
     }).load(this.href + ' #ava img:first', function () {
      $('div.ava img').css({
       width: '100px',
       height: '100px'
      });
     }));
},
function () {
     $('div.ava').remove();
});
</script>

<div id="ava">$_AVATAR$</div>