WorMzy [1] filed a deletion request for palemoon-beta [2]: Upstream does not seem to tag betas any more, opting instead to provide precompiled development builds. Users wanting cutting edge should probably switch to palemoon-git.
[1] https://aur.archlinux.org/account/WorMzy/ [2] https://aur.archlinux.org/pkgbase/palemoon-beta/
