404 error pages: How to diagnose issues, fix them, and improve the design

Users encounter a "404 error page not found" message when a server cannot locate a web page for the entered URL, impacting their impression of the site. While user errors like mistyped URLs or dead links can lead to a 404 error, designers must diagnose and resolve these issues by regularly auditing the site for broken links, coding typos, and server problems. Common causes of 404 errors include mistyped URLs, deleted pages, outdated or moved links, DNS issues, and corrupted .htaccess files. These errors negatively affect user experience and can harm search engine rankings, as search engine crawlers might remove URLs from their index upon encountering 404 errors. Designers can mitigate these impacts by implementing custom 404 pages and ensuring correct redirects, although too many redirects can also affect site rankings.