[AlexBell]

The background:
I am most grateful to Kovid and the team for giving me the ability to convert books to ePub format so that I can read them on my Sony 650. I very much appreciate the ability to take a mobi format book and transfer to my Sony, and have calibre automatically convert it.
But almost all the mobi to ePub ebook conversions I have done have no paragraph indent and no space between paragraphs, and I very much prefer paragraphs to have an indent.
I have used the Tweak utility a couple of times to text-indent: 1em; to the stylesheet.css, and it seems to work. But it was hard to know where to put this; one book has a 'title' class which governed the layout of paragraphs, and the other has a 'calibre7' class which so far as I can tell did the same job - the second book does not have a 'title' class defined in the stylesheet.

The questions:
1. Do the different classes found in an ePub converted by book follow a set format so that e.g. the calibre7 class in one book has the same function as the calibre7 class in another book? If so,
2. Is there a list available of what the various classes do?
3. Alternatively, is it possible to tell calibre before it converts the ebook that it should indent paragraphs? And if so, how?

Regards, Alex