I have been teaching myself html5 and css3. I have read several books and done samples and exercises. The one important topic that I would really like to understand better is fallback in html5 and css3. All the books mention it, and many examples show it in use. But none of them have really gone into a lot of detail.

I think the topic really deserves at least one chapter in a book or at least a few long articles on the web. However I have just spent a morning searching, and while I can find plenty of code samples that use fallback. I can't seem to find any that really lay fallback out in detail.

So far the best article I have found is http://www.noupe.com/tutorial/svg-clickable-71346.html in which the author shows 8 different ways to use SVG with a fallback to PNG and discusses the pros and cons of all 8 methods.

I think I have some idea of how fallback works in a practical sense just by reverse engineering the theory from the examples. But I am worried that I am missing something and that just having it explained would help a lot.

Does anybody know of a site, book or article on fallback that they would recommend?