Using HTML in jQuery UI autocomplete

Add this to your code:

).data( "autocomplete" )._renderItem = function( ul, item ) {
            return $( "<li></li>" )
                .data( "item.autocomplete", item )
                .append( "<a>"+ item.label + "</a>" ) 
                .appendTo( ul );
        };

So your code becomes:

<script type="text/javascript">
 $(function () {
     $("#findUserIdDisplay").autocomplete({
         source: "ui_autocomplete_users_withuname.php",
         minLength: 2,
         select: function (event, ui) {
             $('#findUserId').val(ui.item.id);
             return false;
         }
     }).data("ui-autocomplete")._renderItem = function (ul, item) {
         return $("<li></li>")
             .data("item.autocomplete", item)
             .append("<a>" + item.label + "</a>")
             .appendTo(ul);
     };
 });
</script>

Note: On old versions of jQueryUI use .data("autocomplete")" instead of .data("ui-autocomplete")