It’s always nice to get some friendly feedback from Google, whatever the subject may be. If you’re just starting out in SEO and you have your own website, you may find 404 errors popping up in the webmaster tools console. They can be frightening and you’ll start to wonder if they can negatively affect your site in the search results.
440 errors won’t and can’t hurt your search engine efforts, e.g they won’t reduce your positioning in Google.
However, they can create a bad user experience and will probably tank your efforts of trying to keep a user on your site. It’s best practice to fix them, but they probably won’t hurt your rankings.
John Mueller recently gave us webmasters some friendly advice on Twitter re 404 errors.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) January 3, 2017
Every website has 404 errors, no site is perfect. Therefore, try not to take it personally if you see 404s in your webmaster console.