Clearing Your Temporary Internet Files (Cache)

Instructions can be found at http://www.wikihow.com/Clear-Your-Browser%27s-Cache but if you're using the latest version of Firefox, see these instructions instead:  http://support.mozilla.org/en-US/kb/how-clear-firefox-cache

Be sure to close all browser windows/tabs after clearing the cache so that the change takes effect.

When you reopen your browser, try whatever you did before and all should be well.

And for future reference, whenever you run into a situation where a particular webpage is acting weird or not showing up as expected, clearing your cache (temporary internet files) is generally the fix to try first.  :)

Hope this information helps!