According to this Question...
Embedding a link (or other html) in a JSF message
... and a relating blog post from BalusC...
http://balusc.blogspot.ch/2010/07/using-html-in-jsf-messages.html
... I only have to remove the import and the annotation of FacesRenderer. There is an equivalent in JSF 1.2 though called Renderer, but this class doesn't cover annotations.
Anyway, I get the following error in my Browser:
Attribute escape invalid for tag messages according to TLD
How can I resolve this issue? Because it seems that adding costum renderer and attribute for a component legal.