Martin Splitt of Google, in a rare case about talking specifically about Google rankings, said that he has confirmed that while Google can discover links within commented out HTML code, those ...

Search Engine Land's Guide to SEO Chapter 3: HTML Code & Search Engine Ranking Success Factors explains HTML elements & using structured data.

11 HTML Attributes For SEO & Why They Matter HTML is the foundation of a webpage. Discover the key HTML tags and attributes that are crucial to good SEO. Find out their uses and how to code them.

A link or URL redirection can be accomplished by anyone with administrator access to a page, provided you have the referring link HTML code, and the domain to which the original link points.