A 404 error is an error that indicates that the page was not found by the server and therefore that the page does not exist or no longer exists. The 404 page is often accompanied by a message: 404 error, 404 file not found, file not found or page no longer exists.
Most of the time 404 errors are due to deletions or modifications of URLs and these pages have not been redirected with a 301. It is therefore important when modifying a page to be careful that the page gives access to an existing page, especially when migrating a site. Indeed, even if only the content has been modified, it is possible that the URLs have been modified, it is therefore necessary to set up redirections.
Another cause can be a bad configuration of the URLs by your CMS which can lead to the creation of bad URLs, thus creating 404 errors.
The 404 errors do not directly impact SEO but since the user experience is negative, SEO will be impacted.
In these 3 cases your ranking can be impacted:
- If an important page of your site leads to a 404, your SEO will be strongly impacted.
- If another site has a backlink to a 404 page on your site, it will impact both sites. Ask to update the backlink.
- If you have a large number of 404, the user experience and the scrolling of search engines will be strongly impacted.
Detect a 404 error with Google Search Console
In the Google Search Console, go to "Coverage" in the menu, the console will show you the errors on your site and in particular the 404 errors, as in the example below:
Fixing 404 errors:
Most of the time, you only need to do a 301 redirect to the new page to correct a 404.
If your page has no equivalent on your site, you can :
- Redirect to a close page, a category page for a product
- Redirect to an unrelated page that is not important for your SEO
If your page is permanently deleted, you can set up a 410 redirect.
Be careful, don't redirect too many pages to the homepage, you will send a bad signal to the search engine and lower your SEO.
In order not to affect the user experience too much, it is advisable to customize your 404 page. Of course, this practice does not affect your SEO but it is a good practice recommended by Google.
Finally, 404 errors do not directly impact your SEO but indirectly through a bad user experience. 404 errors can be easily corrected. Check regularly on the Google Search Console if you have any 404 errors.