For anybody who has the same problem. Actually it says in the documentation that one should include the jar "along with the Facelets", which consist of the following jars: el-api.jar el-ri.jar jsf-facelets.jar
I think would be good to mention them by name in the docs.
Anyway, I have a new problem now: I can access the debug.seam page, but the content/type, which is returned is "text/plain" and I don't know how to change it to "html/plain". I added a mime type into the web.xml, but it does not work.
Well a workaround is creating a file "debugFixed.jsp", which contains two lines:
This was already fixed in the latest release of Seam.