Any website you visit consists of thousands of media files, and sometimes it may take a lot of time for a browser application to load all the website’s content. The first time you visit a site, your browser duplicates original values of the website in order to make it load faster next time you visit it. This process is called caching.
When some changes to the website are made, it is necessary to clear the browser's cache, since some values of the website may be saved on the computer, and the browser will keep opening the old, cached version of the website, so the changes will not be seen.
You can find the necessary manual on how to clear the cache in your browser depending on the operating system you are using: