Email gone to white on black...like Incognito. Other features are normal. Then it said Too Many Tabs...???

Email gone to white on black...like Incognito. Other features are normal. Then it said Too Many Tabs...???

Suddenly my email site went from white on black...normal...to black on white.  All of the features under email are black.  When I shut down, reboot, etc. Everything else on the site is normal.  

I had only begun to send some emails and set up templates when it wouldn't let me do anything else...Too Many Tabs????

Appreciate any input.