Such behavior is expected and is not directly related to the RadWindow control. You will experience the same behavior if you don't use RadWindow, but a standard IFRAME
e.g. - try adding the following code on your page and check the result in the browser:
The reason is that such sites have "frame buster" script that checks if the page is displayed in an IFRAME and if so - either navigate the topmost page to the corresponding site or as in Facebook and Twitter - display a message. This behavior however cannot be controlled from our side - otherwise it would be a major security issue.
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