As you browse, your web browser saves some information about websites on your computer. This helps with faster access as it eliminates the need to to download the same resources again (such as images, logos, etc.), each time you re-visit the website. This accumulation of files is called the browser cache. Sometimes this cache can cause problems leading to degraded performance, as it may store outdated or previous version information. That's when you need to clear your browser cache.

Information about clearing cache from most major browsers is available here.