We had a question from a client in California who wanted to know how to create a custom 404 error page in Microsoft IIS. Great question.  Why would you want to create a custom 404 error page you may ask?  Well the obvious reason is to improve the user experience for your site visitors who come across a broken link or an old page that no longer exists and has not yet beem redirected properly.

1. Create Your Custom 404 Error Page - Use a text editor or an HTML editor to create your custom page on your server.  When you create your custom error page, you may want to call it something like /404-error-page.htm or /not-found.htm. 
2. Open Internet Service Manager - From your server’s desktop, launch the Internet Services Manager (usually located at Start->Programs->Administrative Tools->Internet Services Manager)
3. Click the [+] to the left of the server name
4. Right-click on "Default Web Server" (or whatever you may have renamed it as), and click on "Properties"
5. Locate the Custom Errors Tab - Click on the Custom Errors tab (See Image below)
6. Identify the Error that you would like to edit - Click on the number of the HTTP Error you want to make the custom message for, then click "Edit Properties".  In this case, you would want to identify "404" 
7. Use the Browse button to locate the custom file you created ( i.e. /not-found.htm) and click OK. Keep clicking OK to dismiss the windows, then close the IIS window. Note: You can set any page you want to the 404 page.

The reason that you would want to create a custom 404 error page is to help direct your users to a relevant page on your site, whether it is the homepage or otherwise after they have been served up with a page not found error.  You do not want them to exit the site and never come back so by providing a custom 404 error page, you can direct them to beneficial page(s) of content. 

Here are some examples of some creative 404 error pages:
Enquiro’s Page Not Found Error Page 
CNN Page Not Found Error Page 
Sales Force Custom 404 Error Page 
Zilliant Page Not Found Error Page 
Geico Page Not Found Error Page