This is the most important rule of netiquette for this list. Messages about HTML, graphics, servers, and other topics not directly related to writing and editing for online media are not fair game. Likewise, messages about writing and editing for print or broadcast media are not appropriate. The list will be most useful to you as a resource if everyone sticks to the agreed-upon topic. Use a descriptive subject line.
Many people decide whether they want to read a message based on the content of the subject line.
If a thread changes topic mid-stream, change the subject line to fit the new topic. You are more likely to get people to listen to your message if they can associate a name with the words. Be tolerant of newcomers who make mistakes. We were all new to this medium once. Remember, there are real people at the other end of this mailing list.