I remember working a lot with XML a decade ago. XML was large and clumsy and had problems like undefinable ordering of elements for instance. And I haven't actually encountered a single parser library that did not have some strange issue which made it behave outside the spec. Not to mention editors that happily show "<tag\>" while in reality the file reads "<tag></tag>". Good luck debugging the parser with that one. My bad experience with the XML standard is probably the reason why I never bothered with XHTML. Sure, cool idea, but XML, so meh.