Your browser will keep a local copy of internet files to make browsing faster. Sometimes this can mean that your browser does not download the latest copy of files. You can resolve this problem by clearing your browser's temporary internet files, sometimes known as a cache.
The steps to clear your browser's temporary files changes depending on what browser and version you are using. If you're not sure of your browser version, you can visit this site: http://www.whatbrowser.org/en/
Then once you know your browser and browser version you can visit this site to find out how to clear your temporary files: