Creating a custom 404 Page in Sitecore

Nobody wants to see the standard Sitecore 404 page. Thankfully it's really easy to change the error pages a user is redirected to through some config settings.

Your error pages can be pages in Sitecore or static HTML files. For 404 pages I would normally use a Sitecore page, that way content authors can still manage its content. For an Error Page I would recommend a static html file to avoid issues with the Error page potentially error-ing.

Add these to a patch file and update the urls accordingly:

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
<sitecore>
  <settings>
    <!--  ITEM NOT FOUND HANDLER
          Url of page handling 'Item not found' errors
    -->
    <setting name="ItemNotFoundUrl">
      <patch:attribute name="value">/ErrorPages/404.html</patch:attribute>
    </setting>
    <!--  LINK ITEM NOT FOUND HANDLER
          Url of page handling 'Link item not found' errors
    -->
    <setting name="LinkItemNotFoundUrl">
      <patch:attribute name="value">/ErrorPages/404.html</patch:attribute>
    </setting>
    <!--  LAYOUT NOT FOUND HANDLER
          Url of page handling 'Layout not found' errors
    -->
    <setting name="LayoutNotFoundUrl">
      <patch:attribute name="value">/ErrorPages/404.html</patch:attribute>
    </setting>
    <!--  ERROR HANDLER
          Url of page handling generic errors
    -->
     <setting name="ErrorPage">
      <patch:attribute name="value">/ErrorPages/Error.html</patch:attribute>
    </setting>
  </settings>
</sitecore>
</configuration>

These settings are already defined in the web.config file and changing them here will have the same effect, but I recommend adding patch config files as it will make your solution easier to update in the future.