HTML (ver. < 4)
- Defined as a subset of SGML
- So it's theoretically easy to parse
- Not many people stick on standards → parsing got very complicated
- Not really a markup language, did a lot of "design" jobs
HTML 4
- Tried to move "design" over to CSS
- Many elements deprecated
XHTML 1.0
- Defined as subset of XML (no more SGML)