Relpath isn't Valid XHTML
The $relpath as it is used in wiki templates under vBulletin 4 doesn't validate as XHTML Transitional. The & signs aren't properly encoded as &
It seems this problem is also prevalent in standard vB pages, but it's easy to fix with the built-in template functionality. All templates containing:
HTML Code:
{vb:raw relpath}
should replace it with:
HTML Code:
{vb:var relpath}