Hello, I'm Mervi!
An artist, nerd and business sorcerer, dedicated to make world more beautiful and strange with art, illustrations and logos + to help you figure your sustainable business out.
One of the most overlooked aspect of website design and development are the error pages. Common errors on otherwise working websites are 403 and 404. The first one happens when a website visitor tries to get into a page to which they have no permissions. It's a status code 403 Forbidden, which the server sends to the web page. For instance they could try and access a page in the administration area without being logged in to the administration. Or perhaps they have logged in, but don't have the required access to certain parts of the administration.
The latter error, 404 or Not Found happens when the requested page is not found. This can be for several reasons and it's perhaps even more common than 403 error. At least it's the one website visitors recognise. The page can be not found for several reasons. Did you create a page or an article, but then delete it? On the other hand it can be a mistake in how the visitor is trying to access the page. In case they wrote the url themselves they could have made a mistake in spelling. Or they followed a broken link from another site, a link that either has a typo or has gotten broken for technical reasons.
Most self hosted content management systems and blogging systems allow you to create custom error pages and usually have ready made error pages as well. On WordPress the error pages are often created within a theme and on Drupal you can create a custom page and add it to the website information. Additionally there are multiple plugins and modules for creating different types of error pages. In order to find out how your Not Found looks you can go to a nonsense page on your site, such as http://example.com/abcdefg (where example.com is your website address).
The basic error pages offer very little information and just state the problem without offering any solutions. Custom error pages can be pretty much anything. Back in time the error pages used to often included only a text, that most often said something like "Oops, not found". In time this sort of wording was banned by many due to it sounds annoying and rude. To make the page more useful for the visitor landing it you could include a search, list of popular blog posts and other links to your 404 page. If you are really crafty (or find a plugin or module for it) you can create a 404 page which searches for existing pages and articles which have similar address as the broken or non-existing url. Pinterest shows on their 404 page a selection of categories for you to browse. Some websites decidedly go with funny rather than useful. The Rolling Stones' official site for example has a very simple 404 page which features a video of the band performing their song You Can't Always Get What You Want. See what they did there? Funny-funny.
Because 404 errors happen unfortunately often for several reasons as stated above, it's pretty important to make sure the page at least looks similar to the rest of your site. Preferably it would be great if the page would provide some information on what just happened and how to get over with it happening.