Adding underlines to links within blog entries only

My blog is worldwidejeb.net, and I’m a bit of a stylesheet dummy.

I’m trying to add underlines to links WITHIN my blog entries – but not any other links (links on my sidebar, etc).

Whenever I edit my stylesheet to fix this, I can’t seem to do it without adding underlines to EVERY link on the site.

Any clues as to how I should modify my stylesheet? Cheers.