This is a common fix for website errors. Clearing your cookies allows for websites to rewrite the cookie and is much like a good night's rest for a fresh start.
- Press CTRL + SHIFT + DEL on your keyboard while you have your browser open.
- Choose "the beginning of time" to delete everything.
Make sure the options to clear cookies and cache are checked.
- Close all your browser's windows and reopen your browser.
You may have to log back into websites after clearing your cookies.