Use this code, with allowscriptaccess='always' and wmode='transparant' or 'opaque' in the HTML code on the Flash element.
private function click(event : MouseEvent) : void {
getURL(LoaderInfo(root.loaderInfo).parameters.clic kTag);
}
private function getURL(url : String, window : String = "_blank") : void {
var browser : String = ExternalInterface.call("function getBrowser(){return
navigator.userAgent}") as String;
if (browser.indexOf("Firefox") != -1 || browser.indexOf("MSIE 7.0") != -1) {
ExternalInterface.call('window.open("' + url + '","' + window + '")');
} else {
navigateToURL(new URLRequest(url), window);
}
}