Understanding HTTP Status Codes
Every time a browser requests a page, the server responds with a status code. 200 means success. 301 means the page permanently moved somewhere else. 404 means the page doesn't exist. 500 means the server had an error. These codes matter because they tell search engines what to do with a URL. A 301 redirect passes ranking signals to the new URL. A 404 tells search engines to remove the page from their index. Getting these right is a quiet but important part of SEO.