After receiving an email from Boris Zbarky where he said that some components of Gecko are no longer available (allowing me to correct some wrong ideas about Gecko), I decided to download the latest version of the source code to keep me up to date. You can find everything at ftp.mozilla.org (anonymous login). I've just finished to download it and, due to the enormous amount of files and libraries, I'll need a lot of spare time to look through it! Anyway, I'll let you know.