Too Many Characters??

EDIT: it must have been the image URLs, because once I found a site to host smaller URLs the problem went away. This topic can be flagged for deletion or ignored or whatever now!

So I was trying to post an auction thread but it keeps telling me posts must be limited to 10000 characters. I put my post in a character counter and it was only 3.4k (ish).

Does the HTML count as characters? Do image links? That's the only thing I could think of that would be pushing me over, but even then, I can't be sure. Thanks!