Override existing Application Pages with Custom Page - SharePoint 2010

With SharePoint 2010 you can now set your own custom error pages by overriding out-of-box application pages like AccessDenied.aspx, Confirmation.aspx, Error.aspx, Login.aspx, ReqAcc.aspx, SignOut.aspx etc. Various methods like UpdateMappedPage, GetMappedPage have been introduced to facilitate this.