I have a code in edit mode!

I use a Mac. When I try to edit a wiki page, I see a lot of code on the page. This did not happen in the past. Along with all the code, I get the following message: "Unfortunately, your browser isn't compatible. We want you to have access, though, so we recommend you download a compatible browser (e.g., Firefox)" But I have the latest version of Firefox. I've downloaded it several times and this does not fix the problem. I tried using the latest version of Safari and that doesn't work, either.