All the links in the description of the forum categories seem to be broken. They point to https://cern.ch/geant4/support/user_documentation and https://hypernews.slac.stanford.edu/HyperNews/geant4
Those to the main site should now be fixed - the HyperNews links are a WIP as that service is no longer available from SLAC, and the archive needs preparation of a hosting service, which is on the cards.