Is it possible to turn down the fill opacity of an object to 0 in CSS?

Question

I have been trying to make a form that looks like this:

http://designyoutrust.com/wp-content/uploads/2012/09/Sign-In-Widget.png

I already achieved this with Photoshop but I wanna know how to do this with just pure CSS. Thanks! :)

Answer 1

 background: rgba(0,0,0,.2);

You can adjust the last number to something less than 1 but greater than 0 to get exactly what you are looking for