Background Image in a boxed xanga?, Is this possible? Options

[computershateme]

Alright, I'm not quite sure if this is going to make any sense, but i am using this boxed xanga code:

CODE

<!-- begin code provided by createblog.com -->
<DIV align="center" valign="center" style="BORDER-RIGHT: #FFFFFF 1px solid; BORDER-TOP: #FFFFFF 130px solid; FILTER: alpha(opacity=60); OVERFLOW: auto; BORDER-LEFT: #FFFFFF 1px solid; WIDTH: 635px; BORDER-BOTTOM: #FFFFFF 1px solid; HEIGHT: 685px; BACKGROUND-COLOR:
#ffffff">
<!-- end code provided by createblog.com -->

And, as you can see, I changed the top border from 1px to 130 px to get the box centered on the page, and over my background picture, because my picture is centered on the page. Make sense? I want the picture right behind the box.
Now, it looks fine the way it is on my computer, but i noticed on others that when i view my page it's not centered over my background pic, and there're this huge empty block of white where i changed the top border.
So that the box is centered over my pic on all computers, is there any way i can put a background image in the actual boxed xanga code? so that is part of the box and will be behind the words and centered no matter what?
If thats not possible, is there anything i can do to make the box centered over my picture no matter how the internet options of a computer are set up?
*just a thought* cause it looks really bad on every computer but mine