It's a gamble if you try centering something on a background image... I would take the CSS apprroach:
Code:
body {
margin: 0 auto;
}
#container {
background: url('http://blaqk.tylerbryan.com/layout/layout1a.jpg') top left no-repeat;
margin: 0 auto;
width: 850px
height: 567px;
}
/*===>>> Enter your Text Box Data Here <<<===
.textbox {
}
*/