<body>, <head>, and <html> are the required tags. All your webpages should also have the <title> in the head. There should only be one of each and the structure should be as in skeleton.html (Right-click, Save link/target as...).
<?xml version="1.0" encoding="ISO-8859-1"?>
<!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">
<head>
<title> Test Page </title>
</head>
<body>
</body>
</html>