Nope the main website http://developer.amd.com/ works fine, it just seems like any sub-directory like http://developer.amd.com/tools-and-sdks/ just gives a 404. Does it work for you if you go via an external proxy?
EDIT: Interestingly I can get to http://developer.amd.com/tools-and-sdks/opencl-zone/codexl/, but not http://developer.amd.com/tools-and-sdks/graphics-development/gpu-perfstudio/
Ok so the PerfStudio page has just started working for me! The tools-and-sdks page is still not working, but I am unblocked if someone changed something then thanks
Can you try a control + F5 refresh (once again) and let me know if it's working. I had to do that again today as it had cached the 404 but is coming up for me now.