And So I have this code:

<iframe id="theFrame" src="http://localhost" style="width:100%;" frameborder="0">
</iframe>

and also the localhost site loaded within the iframe all right..

however after i alter the src for an exterior website

<iframe id="theFrame" src="http://www.youtube.com" style="width:100%;" frameborder="0">
</iframe>

The web site didn't load.

What did I actually do wrong? I understand which you can use exterior websites within an iframe since Google Image Search achieves this...

How do i get exterior sites to operate during my iframe?

It seems to become a youtube-only problem src="http://www.mozilla.org" works best for me inside your code. If you wish to display youtube videos in iframes, they'll most likely want you to employ "embed" option around the video page?

Your Code is correct, rather In my opinion the network you are attempting to gain access to Youtube on has blocked the youtube.com domain. Are you able to verify this if you attempt another domain?