Update "Does a page need to validate HTML?"

[Jefferydo]

The problem with a blanket "yes" is there are all kinds of validation errors that aren't relevant to 4.1.1 Parsing (Level A). A stuffed page can throw a lot of errors that aren't accessibility related.

4.1.1 specifies four markup requirements:

• elements have complete start and end tags,
• elements are nested according to their specifications,
• elements do not contain duplicate attributes, and
• any IDs are unique..

The course has a page on the topic: Parsing and validity