Let's say you are fed up with typical Access Denied message in SharePoint 2010, and you want to customize it using your own page. It's pretty easy and quite simple to do that.
Steps.
1.Develop your custom Access denied page in Visual studio 2010
2. Deploy to the SharePoint Server.
3.Run the following powershell commands.
Set-SPCustomLayoutsPage –Identity "_layouts/accessdenied.aspx" –RelativePath "/_layouts/custompages/mycustomdenied.aspx
*mycustomdenied page is the custom page.
Happy Share Pointing :-)