The quiz can be found here: XHTML Quiz — ManuelBieh.de (beta). Some things to note:
eXtensible HyperText Markup Languageas the quiz suggests.
blockquoterequires block level element content when following the strict version (and future) of HTML/XHTML.
pelement for a line break is valid, but not correct. It was not clear to me what was meant. That may be due my lack of knowlegde of the German language.
DOCTYPE. Just like XHTML 1.1 Strict as
DOCTYPEdoes not exist. I am therefore unable to answer that particular question as it uses radio controls where I need checkboxes.
DOCTYPEis not an element.
Still a great idea though.