CSS provides an easy way to target browsers on different types of devices, or different uses. For example, the design you produce for a normal desktop browser may not be suitable for a handheld device, or a printer. These are known as media types. There are several media types, and most browsers will generally concentrate on just one or two, depending on what they are designed to be used for. Opera is by far the most versatile, and supports six different media types.
CSS2 allows you to specify stylesheet for specific media type such as screen or print. Now CSS3 makes it even more efficient by adding media queries. You can add expressions to media type to check for certain conditions and apply different stylesheets. For example, you can have one stylesheet for large displays and a different stylesheet specifically for mobile devices. It is quite powerful because it allows you to tailor to different resolutions and devices without changing the content. Continue on this post to read the tutorial and see some websites that make good use of media queries.
Read More for Examples:
http://blog.varadesigns.com/css3-media-queries/
