How to fix the YIKES [iPhone/MAC version]

This will log you out of all your sites. You'll have to log back in. 

Delete history, cache, and cookies

Here's how to clear information from your device:

• To clear your history and cookies, go to Settings > Safari, and tap Clear History and Website Data. Clearing your history, cookies, and browsing data from Safari won't change your AutoFill information.
  
• To clear your cookies and keep your history, go to Settings > Safari > Advanced > Website Data, then tap Remove All Website Data.