How do I hover of the images and get them to change?

I'm trying to image that changes to another image when i hover over it. Unfortunately, no images appear on the html upload. It's just a blank screen. Can someone please help?

The code is below.

Best wishes Dan Collinson

.b-george {

    width: 130px;

    height: 195px;

    background: url("images/beatle.george.jpg") no-repeat;

    margin: 50px;

}

.b-george:hover {

    background: url("images/george.jpg") no-repeat;

}