How to fix Big image as background image in web design?

Hi everybody, I am in a problem of big image-background in css! How can I solve big image as background-image for different wide of window? Please help me.

	background:url(images/img.jpg) no-repeat fixed 50% 50%;


If you need wider support, you could try some jQuery, such as

Another example of the CSS3 method mentioned by Paul is here: