What is semantic markup, and why would I want to use that?

Question

Like it says.

Answer 1

Here is an example of a HTML5, semantically tagged website that I've been working on that uses the recently accepted Micro-formats as specified at http://schema.org along with the new more semantic tagging elements of HTML5.

http://blog-to-book.com/view/stuff/about/semantic%20web

Googles has a handy Semantic tagging test tool that will show you how adding semantic tags to content enables search engines to 'understand' far more about your web pages.

Here is the test tool: http://www.google.com/webmasters/tools/richsnippets?url=http%3A%2F%2Fblog-to-book.com%2Fview%2Fstuff%2Fabout%2Fsemantic+web&view=

Notice how google now knows that the 'things' on the page are books, and they have an isbn13 identifier. Adding additional metadata, such as price and author enables further inferences to be made.

Hope this points you in some interesting directions. More detailed semantic tagging can be achieved using the Good Relations Ontology which is pretty much the most comprehensive I can think of right now.