There are many reasons you may have to occasionally clear the cookies and cache from your web browser. Here's a little trick that works on almost every web browser. Hold down the following keys:
Ctrl+Shift+Delete and you'll get a pop-up. Be sure to select/check Browsing & Download History, Cookies, and Cache.
After you've cleared the history, then close and reopen your browser.
Depending on your browser, you'll get a popup that looks similar to this: