If I create a post in a public group and its link is distributed on social media then anyone that clicks the link has access to it. However, If I change that same group that holds the link to private then it will give a 404 error. If you allow me to have control of my own 404 error page then the problem is solved. Otherwise please display a message that is more useful, such as, "The content that your looking for is there but you must login or be part of that group before you can access it." I want to encourage users to login in or gain request access to that group. As it stands the user will think the link is broken or the content is gone.