Both Google Plus and Gmail are down at the moment with a server error attached to them.
When you visit Google Plus you will see an on-screen message saying, “500. That’s an error. There was an error. Please try again later. That’s all we know.”
The problem is a little different over on Gmail with a message saying, “Gmail is temporarily unable to access your Contacts. You may experience issues while this persists.”
If you clear out your browsers cookies, cache and history and then open up Google Plus again you will get to see the 404 error with the message, “That’s an error. The requested URL was not found on this server. That’s all we know.”
Looks like Google have server issues on a few things, Google Hangouts, G Plus and Gmail only seem to be the problematic services. If you use Google Plus, Hangouts and send and receive emails via Gmail for business then this will slow you down somewhat, we will let you know when all Google services resume.
Are you having problems with Google Plus and Gmail at the moment?
UPDATE: Google Plus and Gmail have been restored.