While testing the new Identity Provider at work, I had an issue with a MS Program, that uses our IDP to authenticate clients. It didn’t understand the CSS nor JS properly.
Digging around and talking with collegues I finally got the hint (thanks Christian) that Windows uses the ancient IE7 mode for embedded websites…
Searching for clues how to remove parts of the page, to get is useable at least, I came accross this post with this magic line:
<meta http-equiv="X-UA-Compatible" content="IE=Edge" />
Now the embedded page looks as it should look! Yay!