Properly formatted 404 Error page
Sometimes when visiting a website, the user sees an Error 404 message. This status means that the requested page is missing from the website, i.e., no page on the website corresponds to the requested URL (404 File not found). This can happen because of a broken link or because the requested page was deleted.
Upon seeing an error page, the user might decide that your site is not working and leave. To prevent this, you need to properly design and place a special website page that visually differs from other pages of your website. When designing this page, use various visual techniques that let the user know that nothing exists at the requested address, for example, different colors or no graphics. Place a site map, a link to the homepage, or a search form on the page, and provide instructions for further actions.
The error message and instructions should be simple, clear, and understandable, for example: “You are looking for a page that does not exist,” “You are looking for a page that has been removed,” “You have typed the wrong page address. Please go to the site homepage or use the search form”, and so on.
To find out how many users land on the 404 error page, install a Yandex Metrica tag on it and use the Session parameters report.
Alert
If a user sees a page with Error 500 message when accessing the site, it indicates a server-side error, and the site is unavailable.
To receive notifications about site availability issues, set up automatic alerts in Yandex Metrica to be sent to your mobile phone or email.