"Not Found" typically refers to an error message displayed when a requested resource, such as a webpage or file, cannot be located on a server. This often occurs when the URL is incorrect, the page has been deleted, or the server is experiencing issues. The most common example is the 404 Not Found error, which indicates that the server could not find the requested page. When users encounter a "Not Found" message, it can lead to frustration as they may be unable to access the information they seek. Website owners can mitigate this by ensuring links are updated and providing helpful navigation options, such as a search bar or links to popular pages, to assist users in finding relevant content.