XML
HTML
User definable tags
Defined set of tags designed for web display
Content driven
Format driven
End tags required for well formed documents
End tags not required
Quotes required around attributes values
Quotes not required
Slash required in empty tags
Slash not required

XML and HTML are different and they both have different
goals. They are designed for different purposes. Some people
think that xml is an advanced version of html and it has
come to replace html. It is not the case. Both will be there
as they are used for different purposes.