@beel: you cant’t put DIVs in wordpress post-paragraphs, as they are embedded in P-paragraphs and wouldn’t validate.
@root: show me how to put a caption under a IMG by tacking a class on IMGs …
i repeat my main point:
why not putting wordpress-posts in DIV-paragraphs instead of P-paragraphs?
disadvantage: lacking default-margin
advantage: much more power for the blogger, by being able to put block-level-elements inside posted paragraphs.
comparing disadvantage and advantage, i would say: DIV-paragraphs are the way to go. there is by W3C-definition no reason to prefer P over DIV for tagging paragraphs.
so i ask for modifying wordpress to output posts with DIV-paragraphs be default or at least adding a switch/an option to change it to your favoured flavor of paragraphs.