What is Netiquette? Simply stated - its network etiquette, that is, the ettiquette of cyberspace. Netiquette refers to the customary set of rules for behaving properly online.
  When you enter into a new 'culture' - and cyberspace does seem to be its own culture - you are bound to make a few social mistakes. You might misunderstand someone and become offended, or offend someone without meaning to. Whatever the case may be, something about cyberspace makes us forget sometimes that your interacting with other flesh and blood people - not just characters on the screen.   So partly as a result of forgetting that people are still real even if you interact with them online, and partly because they don't know the 'rules', well-meaning people, especially newbies, make all sorts of mistakes.

  First rule: Never forget that the person reading your e-mail or post is a person like yourself - with feelings that can be hurt like yourself. Its not nice to hurt other people's feelings, even over the internet. Never post anything that you wouldn't say to reader's face.
   Second rule: Adhere to the same standards of behaviour online that you follow in real life. Most people are fairly law-abiding in real life, either by disposition, or because they're afraid of getting caught. Standards of behaviour may be different in some areas of cyberspace, but they aren't lower than in real life. Be ethical! And don't break the law...Chances are you will get caught eventually.
   Third rule: Know where you are. Something perfectly acceptable in one domain may be totally rude in another. When you enter a new domain or newsgroup, look around before you do anything. Spend a while reading the website or posts, and get a sense of how people who are already there. Then go ahead and participate.
   Fourth rule: Respect other people's time and bandwidth. Its ok to think that what you are doing at the moment is the most important thing in the universe, but don't expect anyone else to agree with you. Post messages to the appropriate newsgroup, and try not to ask stupid questions. Read the f.a.q.'s that they set forth before asking any questions. When appropriate, use private e-mail instead of posting to the group. Dont' post subscribe, unsubscribe, or faq related requests either. If you disagree with the ideas of a particular group, don't waste your time and bandwidth of the members by telling them how stupid they are. Just stay away from them, it saves a lot of time!
   Fifth rule: Make yourself look good online. Check your spelling and grammar before you post or make a website. Heaven knows no one likes to see yo whasup grl fiend, l8ers!! yur website is sew gr8te! AND DON'T TYPE IN ALL CAPS, IT LOOKS LIKE YOU ARE SHOUTING!! Know what you are talking about, and make sense. And most of all, don't post to flamers and definately don't post flame bait.
   Sixth rule: Share your knowledge. Offer answers and help to people who ask questions on the group. If you have received email answers to questions, summarize and post the summary to the discussion group.
   Seventh rule: Help keep flame wars under control. Most people don't enjoy them and they waste space and bandwidth. Don't respond to flame bait, don't post spelling or grammar flames, and if you have posted flame bait or started a flame war, apologize.
   Eithe rule: Respect other people's privacy. Don't read other people's email, or become a script kiddie and think you are all big and bad because you can use someone else's program to do stupid stuff.
   Ninth rule: Don't abuse your power. The more power you have, the more important it is that you use it well.
   Tenth rule: Be forgiving of other people's mistakes. Don't forget, you were once a newbie too!

Adapted from The Rules of Netiquette.