Perhaps because people sometimes forget that there's a human being on the other side of the computer, some people think that a lower standard of ethics or personal behaviour is acceptable in cyberspace.  Of course it is not.
Respect other people's time and bandwidth. The word "bandwidth" is sometimes used synonymously with time, but it's really a different thing. Bandwidth is the information-carrying capacity of the wires and channels that connect everyone in cyberspace. There's a limit to the amount of data that any piece of wiring can carry at any given moment -- even a state-of-the-art fiber-optic cable. The word "bandwidth" is also sometimes used to refer to the storage capacity of a host system. When you accidentally post the same note to the same newsgroup five times, you are wasting both time (of the people who check all five copies of the posting) and bandwidth (by sending repetitive information over the wires and requiring it to be stored somewhere).
Never give your userID or password to another person. System administrators that need to access your account for maintenance or to correct problems will have full privileges to your account.
Never send chain letters through the Internet. Sending them can cause the loss of your Internet Access.
Never assume that your E-mail can be read by no one except yourself; others may be able to read or access your mail. Never send or keep anything that you would mind seeing on the evening news.
Be professional and careful what you say about others. Email is easily forwarded.
If you're doing business online with your credit cards always make sure the Web site is using a secure server to encrypt the transaction. This is an important level of security that will scramble your personal info as it travels around the Net, making it much harder for eavesdropping hackers to pilfer your credit card number. You can tell you are on a secure Web page if the url begins "https"instead of "http,"and you will have a closed padlock icon in the bottom of your browser window.
You should always be aware of basic privacy issues in all your online dealings. To protect yourself, be very cautious of revealing personal information to people you don't really know. Be wary of people you meet in chatrooms who start asking you too many personal details, especially any details that relate to your personal finances.
Be aware that people are not always who they say they are online. That "23 year old single female," may not be 23 or female. If you are going to physically meet someone you've only known online, set up the meeting for a safe public place, and bring along a friend just in case the situation turns out to be not what you expected.