In the tomahawk12 library htmlTag forces tags specified by the "tag"attribute to have separate start and end tags. However HTML specifically disallows certain tags, like 'br' having end tags. Many browsers parse the end 'br' tag as a second tag, rather than an end to the first tag.
Note that the tomahawk (JSF 1.1 version) library does not do this. It has a different implementation of the HtmlTagRenderer.encodeEnd method.