We use the sliding doors technique in CSS with sliced background images as mentioned here to create buttons which are oval shaped and have the color change and press down effect.
Would it be possible to do something simmilar just with CSS but without using any background images.
You can in browsers that support CSS3 property
border-radius(specs)Examples at http://www.css3.info/preview/rounded-border/
In css you should use
a{..}to style the default stylea:hover{..}to style the over effecta:active{..}to style the pressed effect