The word netiquette is a combination of ’net’ (from internet) and ’etiquette’. It means respecting other users’ views and displaying common courtesy when posting your views to online discussion groups.

WebWise Team | 10th October 2012

As you become involved with online discussion groups, you will find that each group has its own accepted rules of behaviour. Many of these have come about because of technical limitations.

For example, on an email discussion list - where not everyone may have seen past messages - it's considered polite to quote from a message you're replying to, so your response has context. It's also considered polite to keep those quotes short and relevant. On a web-based forum, however, where the original messages are visible to all, quoting is often unnecessary.
http://www.bbc.co.uk/webwise/guides/about-netiquette