Web Page Shifts up and loses top part of header

[ChrisjChrisj]

When I view my main page, it looks fine.
It is centered on the screen with some background space
between the top of the screen and the top of the web page.
And has background space to the left and right.

But when I select the sign-up link which is basically:
http://www.anywebsite.com/index.php?command=signup_page

When the sign-up page is viewed, it has moved up to the top of the screen
and loses the top part of the header border.

How can I get it to view exactly like the home page?

To experiment I went to the css file and changed the top margin from 50px to 500px. It only effected the home page, didn't effect the sign-up page at all.

body {
	background-color: #6B6B6B;
	text-align: left;
	margin-top: 500px;

What do you suggest I do to keep the top of the sign-up page from being cut off?

[Centauri]

Rather than use margin on the body, I would be inclined to use padding instead.

If that doesn't work, we would need to see the actual page.