Netiquette: definition & background rules

We all should know how to communicate properly. Communication online has its own rules, too. They are called netiquette.
The word "netiquette" stands for "Internet Etiquette", and  was created to make the Internet experience pleasant for everyone. The most important rule of netiquette is "Think before you post".
Good netiquette means respecting others' privacy and not doing anything online that will annoy or frustrate other people. There are three areas where good netiquette is highly stressed: online chat, e-mail, and newsgroups.  

There is a great number of netiquette rules, but I would like to start with top 5 most important ones.
So they are:
1. The Golden Rule: Treat others the way you would like to be treated yourself. This is an old but a true rule. Avoid obscene jokes, offensive comments and don't send anything that will reflect badly on you or anyone else.
2. DON'T TYPE IN ALL CAPS: It's understood as SHOUTING at people and moreover it hurts our eyes. You can only type in caps a word or two to accentuate something.
3. Use Proper Grammar & Spelling: It is normal when typos and basic spelling mistakes happen because spelling is not always easy, however you should try not to use too much web jargon and to write clear, organized messages.
4. No "Flaming": Sending personal insults and verbal abuse, harassing or insulting someone gives you a bad reputation. This will surely not help you to gain many online friends.
5. Do not Spam: Spam and pop-advertising is not really secure for you.