How do I know which box (AOL, text, HTML) to check when signing up for the newsletter?
AOL is only for America Online users. HTML is for those who can receive e-mail that looks like a web page. Text or plain text is mainly for those with a relatively older system, such as Windows 95. You know you need to switch to plain text if your newsletter comes in with a bunch of html command lines separated by that obscure the newsletter articles.