when you click on the image, it expands enabling you to see the image clearer/better while the background turns black focusing your attention only on the image. Is this a CSS technique or a client side language?
If it is CSS can somebbody provide any good tutorial links please.
That is a jQuery lightbox or what ever other names some producers have given them. There are quite some versions arround. Here is a page with 10 different ones: 10 Lightbox scripts