Some files were moved around yesterday as Realms Beyond has expanded. So, the answer to your question depends on what link you were using to get here.
Things also might be a bit funny as we finalize everything.
http://realmsbeyond.net goes to the "main" Realms Beyond site, which has links to this forum and to RBx game sites. From that page, where I think you were, you'd want to click on "diablo" to get to rbd, or "realms beyond forum" to come here. The change in our file sytem means that, at least for the time being, http://diablo.realmsbeyond.net will also take you to the "general" RB page.
If you're just looking for the old RBD site, it can be found at http://realmsbeyond.net/diablo. Everything is still there, and should still be functional. KoP mentioned it above, but any bookmark of yours that is not working should be fixable by adding /diablo after realmsbeyond net in the URL.