jquery dialog popup window problem

I have this code

 $("#window").dialog({
          resizable: true,
          height: 180,
          title: titles,
          width: 500,
          modal: false,
          buttons: {
              "OK": function () {
                  $(this).dialog("close");
              }
          }
      });

i am able to get the popup pe开发者_StackOverflow社区rfectly but the problem I am getting here is..

On the top of the Dialog box I have 'X' I am not able to see that X on dialog popup's but when I resize my window I can able to see..

what I am doing wrong in this?

Thanks for your all help

Make sure you're including the jquery-ui css:

<link href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" rel="stylesheet" type="text/css"/>