I compared the sources of both sites using WinMerge, and discovered an extra, non-ASCII character in the source of the temp site. It's in the style attribute of the form tag (I highlighted it with orange background and replaced it with an asterisk, see the source snippet below):

<form name="Form" method="post" action="/dnnprod/default.aspx" id="Form" enctype="multipart/form-data" style="*height: 100%;">

That extra character prevents the style attribute to be interpreted, so the form hasn't the full window height, which leaves the body background (#D3D3D3 = gray) visible at the bottom.

The form tag is in the default.aspx. No idea how that character crept in, but I suggest that you ask your provider to copy that file again.

Hope that helps!