Topic: Bug in default templates
PunBB has a minor bug in the default XHTML templates. The 'html' element is missing the required 'xmlns' attribute. The HTML Validator doesn't report on this, because it has some XML limitations, mostly because it validates based on the XHTML 1.0 DTD, which doesn't notice the missing 'xmlns' attribute.
In the upcoming version of the W3C HTML Validator, it will be able to notice the missing 'xmlns' attribute and thus render all existing PunBB installations "invalid". Read more about that here. Thus I would suggest to include the 'xmlns' attribute in the default templates.
I'd also vote for inclusion of the 'xml:lang' and 'lang' attributes, so the used language in the forums is specified (if that information is available somewhere, that is).