so on a forum im a part of it was working then the owner set it to show mailcow when people visit the forum then they removed it so i refreshed my browser updated the device but still see this
There are many ways to do that, I don’t think this is relevant now. Can you see if the forum works for you now? You might want to restart your browser to get your cache cleared.
Richard is right this has nothing to do with discourse. You just have to clear the cache in your Web browser.
The cause of this was a misconfigured reverse proxy on a very much unsupported install. I have a discourse multisite installed on the same server as Mailcow and Nextcloud. I fixed it very quickly last week so it should be working for everyone visiting my discourse sites by now.