[Typo3] customize page content elements htm/css output

[Amr Mostafa]

Hello,

Can I customize the htm/css output from page content elements ?

For example, by viewing source of the generated pages, I notice that for 
the Text content element, typo adds <p class="bodytext">...</p> around 
the text. And for the header it adds <div class="csc-header 
csc-header-n1"><h1 class="csc-firstHeader">....</h1></div>.

How it's possible to change this ?

Thank you.

- Amr

P.S. If this is documented somewhere, It will be good enough to point me 
to the document.