in top of this file
/components/com_k2/views/itemlist/tmpl/tag.php
I wrote
<?php
$taggs = $_GET["category"];
$cat_tag = explode(",", $taggs);
?>
now I have an array with categories id. right?
the next step ... it' more difficult (for me)
I have to work befor this foreach?
<?php foreach($this->items as $item): ?>