After you configure a custom 404 error page when using a Alibaba Cloud CDN or ApsaraVideo VOD, when you request a Web service through a browser, if the requested URL does not exist, the Web server returns the 404 error page by default. This topic describes why the custom 404 page appears.
When the web server returns an HTTP 404 status code, the web page is automatically redirected to the 404 Not Found page. A URL cannot be accessed if the URL generation rules of the web page have changed, the web file is renamed or relocated, or a spelling error exists in the provided URL. When the web server receives a request for such a URL, it returns a 404 status code to notify the browser that the requested resource does not exist. Possible causes of a 404 error:
- When accessing a single resource, if the resource cannot be found and the 404 status code is returned, you will be redirected to the 404 page.
- If the access URL link contains multiple resources and only some resources cannot be accessed normally, the page will not be redirected 404.
- The website cannot be accessed through the requested port.
- The web service extension lockdown policy blocks this request.
- The MIME map policy blocks this request.