How to call the function from another URL page

How to call the function from another URL page?
ex.
192.168.0.90/top.htm:
function foo(){
alert(1);
}

<frameset>
<frame src=”192.168.0.91/left.htm>
…

192.168.0.91/left.htm:

top.foo();
—————————-

but the browser will display the msg of
“you have no the right to do that”

My good friend, who know what’s Happen?

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