For Blog Authors:

N.B. It’s worth noting that some of the short HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. tags (<i> <u> <s> etc) seem to be deprecated i.e. not all new browsers render them, so it’s often better to use the XHTML tags ( <em> <strong> etc) – except on platforms that don’t accept them, of course.

• Basic HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. for Bloggers.
  - from 2007, but excellent introduction
• Basic Blog HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. Language
  - introduction with a table listing TAG-ACTION-EXAMPLE for simple formatting
• Blogger HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. Tutorial
  - typically good introduction from eHow
• Basic HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. tag for bloggers
  - simple list of tags with formatting actions
• HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. Text Formatting
  - W3Schools is the best all-round resource, with widgets that allow you to test the code for yourself on their site – not much on detailed explanations though.

For Blog Commentors

In WordPress, the blog authors can use a wide range of HTMLHyper Text Markup Language - the encoding scheme used to create and format a web document. tags, while blog commentor’s options are restricted to some basic formatting tags. Other blogging systems similarly restrict the markup allowed in comments, in order to limit potential avenues for exploits.

• HtmlHyper Text Markup Language - the encoding scheme used to create and format a web document. allowed in comments #2

Most of the articles listed above offer links to more advanced tutorials at the end of their own tute.