Mike Davidson has an interesting blog posting about the relevance of specific HTML tags in regards to search engine positioning. He created websites with different tag combinations to test how much valid HTML, heading tags, titles and filenames of websites affect the ranking on Google. Some interesting facts:
- Having the keywords in headings such as H1 are indeed important for the ranking of a website
- Using old-style table design with many nested tables on your website has a negative effect on Google, but not as much as some might think
- Google doesn’t really care if your website validates and there doesn’t seem to be a penalty for having broken code
- Things like titles, descriptive filenames and incoming link texts are dramatically more important
Especially the filenames/directory names are important for Google to determine the ranking of a website for a specific keyword. I think that’s one of the main reasons many blogs rank so well: most blog engines have parts of the posting titles in the URL.