it looks like you are adding the contact.php page to the contact_us.php page as an include using require_once() and doing the same with the siteHeader.php page.
this wont work.
the problem is this:
in both the siteHeader.php and contact.php pages there is php code that must come before any HTML output.
the format of the contact_us.php page will be something like this:
other HTML Code
[include the siteHeader.php here]
some other HTML code
[include the contact.php here]
rest of HTML code on the page
so by using require_once to include the site header and contact pages as includes, it will be adding php code to the page after HTML output which is causing the issue you are experiencing.
the work around for this is to use Framework builder plugins. Framework builder plugins will automatically strip the php code that is before the doctype tag of a page and add that code above the doctype tag of the page it is being plugged into to prevent this from happening.
I see in the contact page you sent that you have stripped out the doctype, head, title and other tags, you shouldn't do this when using Framework builder plugins. It is a valid technique in cold fusion and ASP to use includes, but not in PHP.