The maven-theme.css (http://svn.apache.org/viewvc/maven/skins/trunk/maven-default-skin/src/main/resources/css/maven-theme.css?revision=517325&view=markup) contains a minor error. Which makes it not css-standard-conform.
On line 83 h5 is specified like this:
h5 { padding: 4px 4px 4px 6px; color: #900; font-size: normal; }
But normal is no valid value for font-size. Maybe medium or large was meant.
Fixed in svn. I used "medium" instead.
Improvement
Closed
Minor
maven-theme.css invalid css
Fixed in svn.
I used "medium" instead.