//<![CDATA[
function assignHandlers() {// add events via 'Sys.UI.DomEvent.addHandler'
    if ($get('printButton')) {
        $addHandler($get('printButton'), 'click', printDialog);
    }
}
function printDialog(e) {
    window.print();
    e.preventDefault();
}
Sys.Application.add_load(assignHandlers);
//]]>