Interesting thread, Linda!
Funny, I never thought much about it until now - but I'm not very computer literate.
I have noticed though, that when I post using FireFox, I get those large spaces between paragraphs, and when I hit 'preview' to check for errors, I notice it and backspace to close the gaps before hitting 'submit'. IE doesn't do that - it uses single spacing and there are no large gaps.
I'll try RollBones suggestion on how to fix that. Thank you all!