Bug 8522 - Markup errors cause problems with customized CSS

Bug 8522 - Markup errors cause problems with customized CSS

Some includes and templates contained duplicate "header" ids in
the markup. The problem should have come up in routine page
validation, but was obvious when custom CSS was applied.

To test, load any of the affected pages and validate the
generated HTML. There should be no errors about 'ID "header"
already defined." Or, add custom CSS to intranetusercss:

...and confirm that only the topmost menu background is affected.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>