I'm trying to make the following sign up box fluid responsive in CSS.

Here is an example: <http://cssdesk.com/aYLwW>

I would like the input field width to be "flexible" and shrink depending on the page.

You can see from the example when I shrink the window, the button eventually drops down below the input field.

With this in mind, **what should I set my input#iiihuu-iiihuu field width to be** to allow the input field to gracefully resize without any *bumpage*?

Many thanks for any pointers :-D