What is Semantic Markup?
Semantic markup helps in making Web pages more usable from many, novel perspectives. Correct semantic markup makes pages more indexable by search engines and the like. For example, most searchbots privilege headers when determining the main subject of a given page. Good markup also helps impaired visually impaired users, that might not be able to read for themselves and might ask a screen readers to quickly read headers, for instance, in order to find the page section they are actually interested in. Semantic markup is a very important part of Web standards, but it is maybe the hardest to enforce, given its highly subjective nature. Aggiorno can help you in detecting some common semantic errors, such as using br tags to define paragraphs.
See Also