How to make jQuery UI dialog not resizable

Use the resizable option

 var elem = $("#mydiv");
 elem.dialog({
    modal: true,
    resizable: false,
    title: 'title',
    buttons: {
       Ok: function() {
          $(this).dialog('close');
       } //end function for Ok button
    }//end buttons
 });     // end dialog
 elem.dialog('open');