What's the approved version of <br style="clear:all"; /> ?

I cannot for the life of me figure out what the "approved" way is of clearing one element from another. I have images that I need to sit on top of one another and to the right of the page, but I cannot get one to clear the other - I just end up with the images stacked left-to-right!

I've tried inserting all sorts of divs, paragraphs, and breaks using clear attributes both naturally and by way of style elements; either way the WP editor cheerfully removes them from my fscking post as though they were never there. (I did not have this problem in WP 2.3, which I am beginning to strongly regret updating to 2.7.)

Can anybody please tell me what I'm supposed to be doing in order to control element float?