Everyone has seen a "404". It is a server's way of saying: "I got your request, but what you are looking for does not exist here". It is not an error in the browser, the internet or the visitor's computer. It is a response from the site's server, and it almost always has a simple explanation.
What is going on, in plain language
When someone opens a page, the browser asks the server for a specific address, for example /services/cleaning. The server looks for that address. If it finds it, it returns the page. If not, it returns the 404 code. The site is still up and the server is still working: only that address leads nowhere.
The most common causes
The page was deleted or moved and nobody created a redirect from the old address to the new one.
A link is mistyped, on the site itself, in an email, on a business card or in a social media post.
The site structure changed, for example during a redesign, and the old addresses were forgotten.
Someone typed the address by hand and got a letter wrong.
A plugin or a server rule stopped working, and pages that do exist suddenly started returning 404.
When a 404 is normal
A site with a few 404s is not broken. Search engine bots and automated programs are constantly trying addresses that never existed, and the server answers 404, as it should. That harms nobody.
The problem starts when the 404 shows up on pages that should exist: a service page, a product, the contact form, a page that other sites link to or that already ranked well on Google.
Why the important 404s are worth fixing
You lose the customer there and then. People who click a link and hit an error rarely search again. They go back and visit a competitor.
You lose the authority the page had. If other sites pointed to that page, that value is lost when it disappears without a redirect.
You look careless. A broken link in the menu or on the home page suggests that nobody looks after the site.
How to find the 404s on your site
Google Search Console. In the pages section, Google shows the addresses it tried to visit that returned "not found". It is free and it is the first place to look.
Server logs. The server records every request and the response it gave. Whoever manages the hosting can pull from them the list of the most requested addresses that return 404.
Link checking tools. Some programs crawl the whole site and list every link that does not work.
How to fix it
If the page moved: create a permanent redirect (301) from the old address to the new one. Anyone arriving through the old link ends up in the right place, and Google passes on the page's value.
If the page was deleted on purpose: redirect to the most similar page that exists. If there is none, keep the 404, but make sure the error page helps whoever lands on it.
If the error is in one of your own links: fix the link at the source, whether in the menu, an article or an automated email.
If pages that exist return 404: the problem is in the server configuration or in a plugin, and it needs to be looked at by whoever manages the site.
The 404 page counts too
Even when everything is done right, someone will end up on a page that does not exist. A good error page says clearly what happened, keeps the menu and the look of the site, and offers ways forward: the home page, the main services, a search and contact details. It turns a dead end into a detour.
A mistake you should not make
Redirecting all 404s to the home page looks like a quick fix, but it confuses visitors, who were looking for something else and land on the home page with no explanation. Google also treats these mass redirects as errors. Only redirect when there is a destination that makes sense.
If you do not know how many broken links your site has, or if you changed sites recently and are not sure the old addresses were handled, talk to us. We will check and fix them.
Image: Wikimedia Commons, public domain (CC0).