What should I do with the HTML box in the profile page?

I think these other folks explained it all very well. I had trouble getting the hang of it as first myself. All sites are different and set up uniquely it seems. After a while I got used to all the differences and the similarities helped me to understand how to work through them. Enjoy!

Yes you can put your referral links and banners there. Along with pretty much everything else you want. I wrote a Mylot new users guide that contains helps with utilizing your profile here. Also has a lot of other facts and tips about this site. Link to it can be found on my profile, top right.