From time to time, you need to clear your browser cache. This happens here on the forums as well as on other sites such as facebook.
In fact, if you notice a site not working the way that it should, chances are the issue is on your end (your browser cache) and in order to get the site working for you again, you need to clear your browser cache.
How you do that varies a bit, depending on which browser you use. I've created videos on home to clear browser cache for 4 common browsers.