print selected area in javascript

<style type="text/css" media="screen">
.hideonprint {display: block;}
</style>
<style type="text/css" media="print">
.hideonprint {display: none;}
</style>


......................


<div class=".hideonprint">
you can see me now, but you won't see me when printing!
</div>




next --->

onClick="javascript:window.document .tablename.print();"