Modal redirect from site to site - repost

Hi , I want to have a modal redirect popup which I can put on different websites. What it should do is that as soon as I go from url A to url B, it pops up with a message ' you are being redirected'. See screenshot. I will give you login to one of my sites so you can install it for me. But: it should be clear for me how to move it other sites! Also, i want to simply put a picture (JPG) in it, and together with colour adjustment I should be able to change it for other sites!