<script>
    function open_child(url,title,w,h){
        var left = (screen.width/2)-(w/2);
        var top = (screen.height/2)-(h/2);
        w = window.open(url, title, 'toolbar=no, location=no, directories=no, \n\
        status=no, menubar=no, scrollbar=no, resizabel=no, copyhistory=no,\n\
        width='+w+',height='+h+',top='+top+',left='+left);
    };
</script>

<form name="site">
Daftar Site  <input type="text" name="h4nk" id='siteh4nk' value="" style="width:200px" />
        <button onclick="open_child('popup.php','Look Up','800','500'); return false;">...</button>

 </form>