I posted last week about page structure and headers and their relation to SEO, today I would like to clarify something. The point i want to clarify that search engines will not care if you use h1, h2, and h3, they try to extract the featured elements in your page. That is, if you use h1, h2, and h3 and you modify the default styles to have the same font size for all headers and normal text, search engine will not assume that the data inside these headers is featured. You should give your page main header a bigger font than any other text on your page, otherwise, it is not featured on the page, and you are less likely to rank for the keywords in that header. Wait a minute, using a big font size, does not mean you will rank for it, it is one of the many things that you need to do, which i will write about it later.
Thus, your page main header (h1) which is usually close to the body tag should be relatively bigger than h2, h2 font size relatively bigger than h3 and h3 font size relatively bigger than your normal text font size.
If you feel that you need to have more than one h1 header, I would recommend you to have new pages, one for each h1 header.