Will Allah hold me accountable for registering in a forum for magic merely to browse, knowing that I did not participate in it or act upon anything in it?

It is not permissible to go to sorcerers or to enter their websites and forums, or to watch acts of magic; for that entails condoning falsehood and being pleased with it. Rather, one must turn away from it. Allah Almighty said: "And those who do not bear witness to falsehood, and if they pass by futility, they pass by with dignity." (25:72) Thus, everything that is forbidden, it is forbidden to watch; because it is an aid to disobedience and a pleasure in it, and there is no difference between seeing it directly or electronically. What is obligatory is sincere repentance for what has passed.