How does Google use HTML tags to enhance the search engine?

Question

I know that Google’s search algorithm is mainly based on pagerank. However, it also does analysis and uses the structure of the document H1, H2,

Answer 1

Google very deliberately doesn't give away too much information about its search algorithm, so it's unlikely you will find a definitve answer or academic paper that confirms this. If you're interested from an SEO point of view, just write your pages so they are good for humans and the robots will like them too.

To make a page good for humans, you SHOULD use tags such as h1, h2 and so on to create a hierarchical page outlay... a bit like this...

h1 "Contact Us" ...h2 "Contact Details" ......h3 "Telephone Numbers" ......h3 "Email Addresses" ...h2 "How To Find Us" ......h3 "By Car" ......h3 "By Train"

The difficulty with your question is that if you put something in your h1 tag hoping that it would increase your position in Google, but it didn't match up with other content on your page, you could look like you are spamming. Similarly, if your page is made up of too many headings and not enough actual content, you could look like you are spamming. It's not as simple as add a h1 and h2 tag and you'll go up! That's why you need to write websites for humans, not robots.