$("#SelectID option[value='selectValue']").attr("selected",true)
<script type="text/javascript">
$(document).ready(function(){
$("ul.sf-menu").superfish();
<?php global $st;if($st){;?>
$("#edit-taxonomy-3-wrapper").css('display', 'none');
$("#edit-taxonomy-3").val('<?php echo $st->tid;?>');
<?php };?>
});
</script>