No one is giving away free NX, or free mesos. Ignore those people who send you messages asking you to go to phishing websites for these free things.
Example: http://puu.sh/Vt1A.jpg (it's just a picture)

You most likely will NEVER have a Steam admin contact you. As moderators, we will try to do our best to deal with these people and remove them. If it is too late, and you have already fallen for this, change your password immediately. Keep your account safe!