The number ‘404’ is one of those obscure terms from IT technology which is understood even by people with relatively little IT experience. Anyone who’s used the web for any length of time knows when that number appears, something’s gone wrong. ‘404’ is one of many ‘response codes’ from a web server which tell the browser what it understands by the request (the web address, or URL) that’s been made. These codes are just machine communication, of course – we don’t normally see them – but in the case of ‘404’, we often see it, because it means the server doesn’t understand the request and may not have been programmed to do anything else except to display that code.
What does the error message on your website say? Type in the domain followed by some rubbish (e.g https://www.bmon.co.uk/xxxxxxx). I’m sure you won’t get a message saying ‘404’ – most websites have something better set up – but is the error page actually helpful? Incorrect URLs often come from links on other sites, and if people following them just get a message that says ‘page not found’, they may well go back and continue where they left off, and assume that the whole site or company is no more.
There are many codes other than ‘404’. When the server understands what’s wanted, it sends back ‘200’ or one of a number of codes starting with 2, not that the visitor would ever see this. For those of us who manage websites however, the codes ‘301’ and ‘302’ are perhaps the most important. These tell browsers that the URL requested is understood, but the server is going to send them somewhere else instead. They are redirections, set up by the website manager on purpose, and they’re critical in SEO.
We set up a ‘302’ when we want to send people to another page for a short period, but will be reverting to the original page in the long run. An example might be if a product is currently unavailable, and we want people to see that, but we don’t want the search engines to think the page with that announcement is a permanent replacement for the original product page. The search engines understand this, and will rank the replacement page as highly, for a while at least.
Most important of all is ‘301’. We set this up when we want to send people to a page which is a permanent replacement. It could be because the original page has been deleted; because there’s an external link which is incorrect; or because we’ve set up a shortened URL for people to type in. Again, search engines understand this perfectly and will adjust their records quite quickly.
When you redesign a website, it’s usual for most or all of the URLs to change. If you don’t ‘301’ redirect every page from the old site, you’ll kill years of work improving your search engine rankings. It’s almost criminal for a web designer to omit to do this, and yet we see it happen again and again. Make sure you never allow it.