Ah… a teachable moment. The reason it doesn't work on twitter is because they serve their page with the following header:

    X-Frame-Options:SAMEORIGIN

You can also use the following value:

    X-Frame-Options:DENY

This prevents a different site from framing your site. Increases security against click-jacking phishing a bit. Modern browsers will recognize it and enforce it. Super easy to implement and recommended for all of you web app developers out there.