You will have to use javascript. All you need is an event listener on the login button, then you check the value of the input field and redirect. This is simple enough to do it with plain javascript, but it's even easier with jQuery. It should be something like this (but I haven't test the code).

$('.orangebutton').click(function () {
    if ($('input:password').val() == "hello") {
        window.location.href = "http://stackoverflow.com";
    }
});

Of course you have to include jquery library and make sure that the dom is loaded.

If you want to simulate someone clicking on a link, use window.location.href

If you want to simulate an HTTP redirect, use window.location.replace

You can use assign() and replace methods also to javascript redirect to other pages like the following:

location.assign("http://example.com");

The difference between replace() method and assign() method(), is that replace() removes the URL of the current document from the document history, means it is not possible to use the “back” button to navigate back to the original document. So Use the assign() method if you want to load a new document, andwant to give the option to navigate back to the original document.