To give another deviant a direct link to this FAQ answer, use the following code in your comment or forum post:
Can I advertise on deviantART without purchasing an official advertising package?
Members are not allowed to use their deviantART account directly for any sort of for-profit third party advertising whatsoever.
Members who attempt to install click-through links, banners, promotional materials or third party advertising of any sort in their Journal, profile page, signature, art submission or any other area of the site could have that advertising removed without notice when it is brought to the attention of the deviantART staff and their profile could be suspended or banned as a result.
All advertising efforts which go beyond deviants promoting their own personal and private endeavors must be directed through proper channels. Advertising products offered by deviantART can be found at this page; [link]