You can not disable print functionality on browser, but you can control the content of print using window.onafterprint and window.onbeforeprint. Below is sample
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
Untitled Page
</title>
<style>
@media print
{
.hide
{
display:none;
}
}
</style>
</head>
<body>
<form name="form1" method="post" action="WebForm4.aspx" id="form1">
<div>
</div>
<div>
<iframe src="http://www.w3schools.com/css/css_mediatypes.asp" id="iframe1" class="hide"></iframe>
</div>
</form>
<script>
</script>
</body>
</html>