I just found the solution for the problem with the server certificates of gfx5, gfx6, gfx7 and gfx8.
Load the hotmail page. Than open Activity (Alt apple A). You can see the red marks of the 4 servers. Click a line of one of the servers and safari will show you a screen about the server certificate problems and ask you how to proceed. Go to the item trust, open it and change the setting to 'always trust'. Your system will ask you for verification and than the item will load.
Do this with each of the servers with the certificate problem once and proceed alike. Than the page will open as before!!