Render HTML in javascript function

<a href="#" onclick="NewWindow('pics.php?image=interior10','interior10','260','315','no','center');return false"><img src="thumb/interior10_thumb.jpg" alt="interior10" border="0"></a>

<script type="text/javascript">
           var fullURL;
           var xxx;
           fullURL = parent.document.URL;3
           xxx = fullURL.substring(fullURL.indexOf('?')+7, fullURL.length);
           document.write("<img src=art/" + xxx + ".jpg />");
       </script>