print iframe content

[ddr18]

<iframe name="myFrame" id="myFrame" width="600" height="400" src="http://www.w3schools.com"> </iframe>
<input type="button" value="Print" onclick="printFunction(myFrame);" />

<script>
function printFunction(iPrint)
{
iPrint.focus();
iPrint.print();
}
</script>

here in src if i give link like [w3schools.com...] i am not able to print iframe content. but if i give it as www.w3schools.com in the iframe an error msg is being displayed and im able to print it. could u help me in this.

[Andy Langton]

Is the iframe on the same domain as the parent page? If not, security settings are likely to be preventing this from working.