What are the character encodings that are guaranteed to work properly for an XHTML document?

Primary difference between XHTML 1.0 and XHTML 1.1?

Complete list of XHTML versions?

Correct formatting of a horizontal rule?

Which line will be allowed by an XHTML parser?

Which is incorrect with regard to the '' tag? What tag is used to store the description of the document? What does DTD stand for? What XHTML DTD is used most often? Correct application of a class? Who wrote the current XHTML standard?