H1/H2/H3 …all the way down to H6 tags were initially meant not for formatting but in order to help define the hierarchical structure of a website. These days they are mainly used to create a nice visual guide to the most important heading, the next most important and so on which does pretty much the same thing for human visitors. Its important to get it to work for search engines too.
Imagine for a moment that your webpage is an outline and the topic of your outline is the “title” of your page (the one in your title tag) and the H1 tags are your first level topics under your title. Now H2 tags are sub topics that support whatever is in H1. H3 support what is in H2 and H1 and so on all the way down to H6 (if you have them).
Notice that the overall subject and keyword being targeted is “Blackberry 8900 ″ (which is the keyword in the title). H1 tags such as “Blackberry 8900 features” and “Blackberry 8900 accessories” all support the main subject. Then, supporting the H1 tags are the H2 tags.
Make sure however that the supporting content which is the meat of the webpage is well written, and contains important information which is directly relevant to your topic. Always keep in mind what sort of information people who are searching for “Blackberry 8900 ″ are expecting to find. If within 30 seconds, they can’t find what they’re looking for in your webpage, they will leave your site immediately.