It may mean your browser cache needs cleared. Each browser has a different way of clearing the cache, consult the browser for direction to clear your cache.
Your browser is using part of the device hard disk space (called your browser cache) to store temporary files used to display recently visited web pages. These may be html files, CSS style-sheets, scripts, images, or multi-media content. Browsers use temporary files to speed up the time it takes to load a page when browsing the internet especially if you have a slow or limited internet connection.
Your browser is constantly checking to see if a content has been updated since you last used the page. If the content is new, the browser will download the content again. If you go back to a page you visited during the browser session, it is likely that you are seeing a stored page.
As you can imagine, the browser cache can get large and take up space on your hard drive, with files you no longer need. One sign that your cache is full is when your browser does not download a fresh copy of a page. When you clear the cache, you will notice fresh pages and corrected data or formatting. You are freeing up space on your hard disk which will allow your system to store temporary files efficiently.
Your cache is also storing the websites you have visited in the past. This may be a privacy concern, depending on who has access to your computer.
You can set the browser to automatically clear your cache or clear it on demand. Check each browser for all the options. Regular browser cache clearing is part of best practices for browser maintenance.