<iFrame> and HTML-box variable profile

I’m trying to show a web site in html-box by using <iframe> tag, but it doesn’t work. Is my approach correct?
Usually it works, but when i put it to html-box in ip-symcon, it doesn’t.

<iframe src=„http://www.ip-symcon.de“>

Hallo
Are you using SSL with your Webfront ?

Yes, I’m using SSL.

You cannot use „HTTP“ inside „HTTPS“. ( Mixed Content )
Look here :
https://developer.mozilla.org/de/docs/Sicherheit/MixedContent

maybe <embed src=„www.example.com“ />

It works with all my external sites.

Regards
Manfred