How do i center this header automatically?????? Options

[deejay21]

Hello im trying to center my header automatically no matter what the screen resolution is set at on the viewers pc. how do i do it???? here is what i have so far..

<div class="masthead"><span></span></div>


<style>

body {margin-top: 180px; }

</style>
<style>

.masthead {width: 800px; height: 169px;
position: absolute; margin-left: 0px; left: 12%; top: 10px;
background-image:url(http://i1021.photobucket.com/albums/Header.jpg);}


</style>



Oh I just want it to automatically center horizontally and stay on top of the page... Thanks Does anyone know how???

Reason for edit: Please use the Edit button instead of double-posting. - Mike