Remove your database
$ sudo rm -f /var/lib/pacman/sync/*
Then rerun pacman
$ sudo pacman -Syyu
If that does not work either it could be a mirror issue and you should update your mirror pool and list (servers respond with a 404 page on errors) - you can check the content of the community.db file - it should not contain any html code
$ less /var/lib/pacman/sync/community.db
Rebuild your mirror pool and mirror list
$ sudo pacman-mirrors --continent
the rerun pacman
$ sudo pacman -Syyu