How to Customize Error Page, Page Not Found and Access Denied in SharePoint 2010

There are many ways to customize these pages for example you can customize by code by creating a feature at web application scope or you can do it by power shell so let’s see the simple way.

First create three pages and place them in this path
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\1033\
Custom_Error.html
Custom_NotFound.html
Custom_AccessDenied.html

Note: if you have multilingual site you need to place these pages in their language folder for example forArabic
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\LAYOUTS\1025\

Second Open SharePoint 2010 Management Shell with Farm Administrator User
Now For Custom page Not Found runs the following Power Shell:

$webApp = Get-SPWebApplication http://test 
$webApp.FileNotFoundPage = “Custom_NotFound.html” 
$webApp.Update() 

For Custom Error Page, Access Denied page,.. All pages listed in the below image

Run the following Power Shell:

$webApp = Get-SPWebApplication http://test
$webApp.UpdateMappedPage([Microsoft.SharePoint.Administration.SPWebApplication+SPCustomPage]::Error,"/_layouts/1033/Custom_Error.html") 
$webApp.Update()