Netiquette Rule #4: Be yourself

Be yourself online because you are not anonymous online and others users are real people too. Do not say or do things online that you would not do in reality because you cannot be taken seriously if you do. Your online image is important. Don't ruin it by being someone you're not.

Trolls and Ghouls are examples of people who are not being themselves online. Trolls are people who write inflammatory remarks about others in blog comments to get a reaction. There are other characteristics of trolls, but that is the most common. Ghouls post graphic pictures of accidents and other tragedies online.

Screen shots and routine archiving may save data you deleted indefinitely. This means anything you write on the internet could conceivably be saved somewhere for all eternity.

(Source: Netiquette Rule #4: Be yourself)