Cross-Site XMLHttpRequest in Firefox 3
ajaxian.com/archives/cross-site-xmlhttprequest-in-firefox-3
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
John Resig has written up documentation of Cross-Site XMLHttpRequest that discusses the W3C Access Control working draft which Firefox 3 implements.