I'm writing in reference to your Physics Stack Exchange account:
We noticed that a substantial proportion of your posts seem to exist only to promote your website. Specifically, in the past 3 months 39 of your 62 comments have been links to Physics Overflow. The help center explicitly identifies this sort of participation as inappropriate (emphasis added):
Be careful, because the community frowns on overt self-promotion and tends to vote it down and flag it as spam. Post good, relevant answers, and if some (but not all) happen to be about your product or website, so be it. However, you must disclose your affiliation in your answers. Also, if a huge percentage of your posts include a mention of your product or website, you're probably here for the wrong reasons. Our advertising rates are quite reasonable; contact our ad sales team for details.
This sort of excessive promotion brings down the overall value of genuine recommendations for everyone on the site, and it unfairly takes advantage of the community we have built up around legitimate, non-promotional questions and answers. In light of this behavior, we have elected to place your account in timed suspension. Due to your previous suspension history, the suspension will last for 365 days.
Physics Stack Exchange moderator
Message Number: 469
Also see http://chat.stackexchange.com/transcript/message/18499535#18499535