You have in some shape or form, had advertisement somewhere. Whether it was a post, thread, signature, or your biography info.
Please remember even if you don't include www. or .com, .net, .org or any sort of ending for a website, as long as you provide a name, you will be banned. If the link is censored, you'll be banned for that as well, because its an attempt to post an outside link, or you did post it but it was already blocked.
Next time, be careful.