html issues in maven plugin goal report

There are html issues with the goal report of the plugin documentation caused by the site plugin, see attached screen shot.

I've also attached a test project, which should reproduce this. I see this issue with m-site-p 2.1 and later, but not 2.0 or 2.0.1. I guess something was changed in the release of 2.1.
Also note that this issue is seen with m-site-p 3.0-beta-3 (haven't tested beta-1 and beta-2, but I assume it exists there as well).