- well formed content: HTML (with characters properly escaped, tags perfectly nested and closed), images, audio, video, etc. Each piece should specify its media type.
- creation date
Via: Mark Pilgrim: The W’s of Weblogging, which offers a further discussion.
This is analogically to the so-called »big W’s« of journalism, which are »What, When, Where and Who« (in different orders), or even a phonecall to »999«.