[Typo3] change header sizes

[Christoph Koehler]

Hello!

I know this is probably asked a lot, but I couldn't find anything about it:
How do I change the different (header) layouts?
I would like to have one big header at the very top of the page, appearing  
only once (h2) and all the individual content item headers I would like to  
have in h3 or h4. How would I do that??

Thanks a lot guys!!

Christoph