Nobody wants error codes on their websites. What do most of us do when we come across them? We go somewhere else. So if you ever see one on your own site, what does it mean?
Sometimes the codes are ‘client side’ (the visitor has the problem) and other times ‘server side’ (the website has the problem). The most famous, of course, is the ‘404’ error code. This means the page or document that the visitor has requested can’t be found. It could be due to a mistyped web address, or an incorrect link, or – most commonly – a link to an item that’s been renamed or removed. As we can’t stop some of these happening, it’s important that we have a good ‘404 page’ which is delivered to the visitor. Take a look at your own (just type in a page on your site that doesn’t exist, like bmon.co.uk/junk) and make sure it’s helpful.
Other ‘400 series’ error codes include 400 (corrupt request), 401 (insufficient authorisation), 403 (no permission) and 408 (request stopped before delivery). On the server side, if you see a ‘500’ it indicates bad communication with the server; ‘502’ is serious server connectivity problems, ‘503’ shows when the website is offline and ‘504’ means the server is taking too long. If you see those on your own site, even temporarily, I’d make enquiries about why, and how it could be prevented in future.