As long as the framed page is on the same domain (or on a sub-domain, and you're setting document.domain), you need to access the contentWindow property of the frame element. For example:
$("#myFrame")[0].contentWindow.myFunction();
// or, if jQuery hasn't made you lazy
document.getElementById("myFrame").contentWindow.myFunction();
Most browsers also support contentDocument, but Internet Explorer doesn't. If your framed page is on a different domain then you'll get an Access Denied error.
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