Adding button pressed effect using css

[bylghyn]

I am trying to add button pressed effect to a button with an image. Here is the css\[code\]input.happy { background-image url(/img/happy.png) background-color transparent background-repeat no-repeat border none width 64px height 64px margin 10px cursor pointer border-radius:8px -moz-border-radius:8px -webkit-border-radius:8px box-shadow: 0px 3px 5px #000 -moz-box-shadow: 0px 3px 5px #000 -webkit-box-shadow: 0px 3px 5px #000}input.happy:hover { position:relative top 3px color #fqq box-shadow none -moz-box-shadow none -webkit-box-shadow none}\[/code\]The effect is shown only on hover. How can I change it so that it is shown when it is clicked. I added something like \[code\] .pressed { position:relative top 3px color #fqq box-shadow none -moz-box-shadow none -webkit-box-shadow none }\[/code\]and changed the class to .pressed on click. But it is not working. Any suggestions