<body bgcolor="#000000">
<table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td valign="top">
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<!--Head Contents Snipped for brevity-->
</head>
<body>
when you include header.php you get all the standard XOOPS Header and Sidebar information, so adding a second body tag is unnecessary. The first line should actually be the <!--DOCTYPE --> line.