Cannot fix position of simple dialog on change of screen resolution(like desktop browser and mobile browser)

[nikstux]

Hello ,
i am using simple dialog in my jquery mobile application. i wanna support all devices and desktop browser. right now i am changing dialog content dynamically like

HTML Page:

        <div class="form">
             <!---different field customize -->
        </div>
        </div>

my script is
$('#id1).simpledialog2({top:mytop,left:myleft});

here i am setting id1 content as dialog content. but everything works fine but when i change resolution of screen then it changes position of dialog on left or right side. sometime out of the screen.. can u suggest how to fix position of dialog at center irrespective of screen resize and resolution.

please help me out ...............................!!

Thanks,