Calic0cat

Oh hey, internet-html-savvy person, while we're on this subject... I have a sort of 'trivia' question about that sort of thing that's been bugging me for ages, in the 'huh, how odd' sort of way. I noticed it in my own stuff some time back, and thought it was something I was doing, but I've since seen it in other stories. What is it with the word 'expression' that makes some kind of html thing put an under-score in front of the word? I see it on archives all the time, and I'm guessing it's some kind of conversion deal? O.o