<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>