If you are allowed to change the code of the document inside your iframe and that content is visible only using its parent window, simply add the following CSS in your iframe:
body {
overflow:hidden;
}
Here a very simple example:
This solution allow you to:
Keep you HTML5 valid as it does not need scrolling="no" attribute on the iframe (this attribute in HTML5 has been deprecated).
Works on the majority of browsers using CSS overflow:hidden
No JS or jQuery necessary.
Notes:
To disallow scroll-bars horizontally, use this CSS instead:
overflow-x: hidden;