Security error accessing url

public function login(_strippedName:String, _userPassword:String){
    userName=_strippedName
    userPassword=_userPassword
    var params:Object = new Object();
    params.username = userName;
    params.password = userPassword;
    service = new HTTPService();
    service.url = login_string.login
    service.method = "GET";
    service.addEventListener("result", httpResult);
    service.addEventListener("fault", httpFault);
    service.send(params)
}
public function httpFault(event:FaultEvent):void {
    var faultstring:String = event.fault.faultString;
    Alert.show(faultstring);
}