How to set the custom Access Denied page in Sharepoint 2010?

We need to follow the below steps to apply custom Access Denied page replacing the OOB application page.

Steps:

1) Create a new Application Page and name it based on your choice(for example AccessDenied.aspx)

2) Deploy this Application Page in to a different folder under Layouts, so that it wont conflict with OOB default.aspx page in the layouts folder

3) Once the page is deployed run the below powershell command/code /script to set the custom page as the login page

$WebAppURL= read-host "Enter the web application URL to which wish to set the Custom Access Denied Page"
Set-SPCustomLayoutsPage -Identity "AccessDenied" -RelativePath "/_layouts/Login/AccessDenied.aspx" -WebApplication $WebAppURL

How to apply custom login page for sharepoint webapplication

In order to accomplish this we need to follow the below steps:

Steps 

• Create a new Application page and deploy the page in a different location in "_layouts" folder. for ex: "_layouts/login"

• We need to execute few powershell commands to replace the outofbox login page to the new page that we created. For easy use I have written a powershell script to execute set of commands at once.

• Create a powershell script and add the below code

1:  Add-PsSnapin Microsoft.SharePoint.PowerShell  
2:  $WebAppURL= read-host "Enter the web application URL to which wish to set the Custom Login Page"  
3:  Set-SPCustomLayoutsPage -Identity "Login" -RelativePath "/_layouts/Login/Default.aspx" -WebApplication $WebAppURL  
4:  Remove-PsSnapin Microsoft.SharePoint.PowerShell  

• The above script will prompt for application url for which you want to set the custom login page.

• we need to make the below change in Web.config along with the above script execution

   <authentication mode="Forms">
      <forms loginUrl="/_layouts/login/default.aspx" />
    </authentication>

Note: we need to follow the same process above in order to apply custom Access denied page. 

1:  Set-SPCustomLayoutsPage -Identity "AccessDenied" -RelativePath "/_layouts/Login/AccessDenied.aspx" -WebApplication $WebAppURL