I need to clarify one thing. I want to sign up around 20 top webmaster forums and I would make 5 posts each per day. I wan to sell some thing in visitor message Can I sell any product in visitor message, it can be designed a little as well and the product is related to webmaster then it would be good. What do you say?
It can be considered as spamming. It will be better if you start a thread to sell your product/service
The best way to use forums to sell products is to have a link in your signature. NEVER directly sell anything in posts! You need to post comments to threads, but not crap comments! You need to interact with others on the forums by answering questions, asking questions and posting informative threads that will benefit readers. Once you start interacting in the forums people will naturally look at your signature to learn more about you.
So you want to spam people and make fool of yourself - good plan . You'll get banned - well maybe except on DP
You can sell directly in your posts but you need to be a master of a written word If you just openly sell you may get banned or whatever but if you know how to write you will sell.
These guys are right, Visitor Messages are not for selling, if the forum has any area for doing this - perfect, otherwise be very careful. It happens a lot on our forum due to the nature of it (Product Forum) and I wouldn't accept it. If they/you contribute to the forum and do it logically as part of a reply, then I have no problem.