I am writing a small client application with ExtJS that reaches out a web service out there in universe. My problem is, when user enters wrong credentials, server throws a 401 exception. I am handles it
callback: function (records, operation, success){
    if (operation.error.status == 401){
        filedset.setInstructions("Invalid credentials");
    } else{
       //handle other exceptions
    }
}
But my custom message is overridden by browser popup asking for credentials. How can I suppress that popup. I have no control over server side.