1 Jesse James Garrett, who coined the term Ajax, claims that it is not an acronym. Pretty much everyone else in the world believes that it is.
Referer is not a typo: The W3C standard itself misspelled the word.
3 RFC822 and others provides more detailed information on what characters are allowed in different parts of an email address
4 Security researcher Robert Auger gave a well-received and comprehensive presentation at Black Hat 2006 about using RSS as a vehicle for injecting malicious content.