Definition: A 404 error, often referred to as “Page Not Found,” is an HTTP status code indicating that the server could not find the requested webpage or URL. This error often occurs when a link points to a page that has been deleted, the URL structure has changed, or the user has mistyped the web address. While the server is reachable and functioning correctly, the specific page in question is not found. To improve user experience, many websites customize their 404 error pages to provide helpful information, links to main sections, or a search bar to guide visitors back to relevant content. Regularly checking and addressing 404 errors is essential for maintaining website health and SEO value.