I was just thinking it might be cool to have a service that site owners could include via JS that would ensure that the content in a div is the content seen by

I was just thinking it might be cool to have a service that site owners could include via JS that would ensure that the content in a div is the content seen by the user. It could have a little stamp that says "Verified by SuchAndSuch" in the corner of the div. Should I try to make this? Any obvious issues? Is it worth it?