https://www.mozilla.com/en-US/firefox/5.0beta/releasenotes/ The "Contributed Builds" section links to http://releases.mozilla.org/pub/mozilla.org/firefox/releases/ , which does not have any 5.0 Beta directories.
A mirror appears to have a 5.0b2 directory there.
Christian, what do you think?
Release notes for 10.0beta and newer look differently, so there is no contrib link: https://www.mozilla.org/en-US/firefox/10.0beta/releasenotes/
Aleksej: Do you want to close this bug then?
If that’s a definite change of all affected release notes…