Players have been warned by the Football Association that they will crack down on improper comments on Twitter and other social networking sites.
Liverpool's Ryan Babel last month became the first player to be sanctioned for comments made on Twitter when he was fined 10,000 for posting a mocked-up picture of referee Howard Webb wearing a Manchester United shirt.
Arsenal's Jack Wilshere last week escaped action after complaining of "inconsistent refereeing" on his Twitter account, and the FA have now made their policy clear.
An FA statement read: "The FA has issued clarification to participants relating to the use of social networking sites, including, but not limited to Twitter, Facebook and internet blogs.
"Participants should be aware that comments made on such sites may be considered public comment, and that further to FA Rule E3, any comments which are deemed improper, bring the game into disrepute, or are threatening, abusive, indecent or insulting may lead to disciplinary
"Comments which are personal in nature or could be construed as offensive, use foul language or contain direct or indirect threats aimed at other participants are likely to be considered improper."
Players have also been warned that even though they believe their postings are only visible to a limited number of selected people they may still end up in the public domain.
"Consequently, care should be exercised with regards to the contents of such postings," says the statement.
"In addition, we would remind participants that social networking postings could also lead to civil proceedings being brought by affected parties."