Custom Error Pages and search engine optimisation
What is an Error Page and how does this affect SEO?
Error pages are standard server response pages created due to an issue or problem in processing your web url request. When you type a web address (url) into your web browser bar and hit enter you are attempting to contact the server that hosts the web site for that particular web address.
If the server is unable to understand or process this address you will be greeted by an error page. The standard internet explorer 404 Not Found error page looks like this,
“Error Pages - Servers response to an incorrect url request or other problem preventing correct display of the target url”
The 400 error - Bad Request
The 400 error page response is a rare error that occurs when a "Bad Request" is made to the server by a web browser. This error means the server does not understand the request that is being made to it.
The 401 error - Unauthorised
The 401 error page response is quite a common error to come across. Certain web sites and web pages require a user to log in or register in order to be able to view the content. This is the error page that will be returned if you enter the incorrect log in details or none at all.
It is basically denying you access to the password protected web pages of the web site you are attempting to navigate.
The 403 error - Forbidden
The 403 error page commonly occurs when a default landing page is not present. If you just entered a web url eg www.degalseo.co.uk then the server handles this request by taking you to the top level default home page - in our web site instance www.degal.com/index.html - if through bad web site design this default page is not defined then this error will occur.
This error can also occur if you attempt to navigate a website's folder structure directly yourself or if a script request is denied by the web server.
The 404 error - Not Found
The 404 Not Found error page is probably the most common error page. It occurs when a page url request cannot be found due to server downtime/non existence of the page/a user types an address in manually incorrectly.
This error can also occur if you change the structure of your web site and the search engines still have index listings of your old site pages. In this instance the standard 404 error being served will eventually lead to the old pages dropping out of the search engines or the visitors via these dead links not seeing your company web site as expected!
The 500 error - Internal Server Error
The 500 error page is a non specific error that can either be with the server itself or from a web script that the server is attempting to instigate. Ensuring a stable hosting platform for your web site and checking any scripting you use can prevent this error from occurring.
Custom Error Pages the Theory
There is no such thing as a search engine friendly custom error page. The process in replacing the standard error pages with custom ones is actually a form of page forwarding. By serving your custom error page you are actually returning a positive server response code as opposed to the negative error code so technically it is no longer an error!
What this means for SEO in practice is the search engines will begin to think all incorrect links actually only refer to the same single new page - as a result the old links will naturally become less important in the SERP's. However they may hang around longer than if the standard error was displayed so for SEO purposes custom error pages are a good idea.
Custom Error Pages for Web Usability
As mentioned in our optimised page content page the goal is to provide relevant content to all web site visitors - real humans & search engine spiders. Now for a real human they gain absolutely no benefit to a standard error page. They are likely to only hit back and if they found your site via a SERP then they return to the search engine results and likely choose the next available result - one of your competitors!
If you have a custom error page set up then you can alert the user to why they are not seeing what they expected to, plus you can then offer them links to your site or sections that you think will be of relevance to them.