Media Queries continues to frustrate web developers just as much as they are exited. CSS3 brings tons possibilities, and solves many many problems, but it comes with a lack of support in old browsers, specially in Internet Explorer.
The V3C definition of the media query is:
A media query consists of a media type and zero or more expressions that check for the conditions of particular media features. Among the media features that can be used in media queries are ‘width’, ‘height’, and ‘color’. By using media queries, presentations can be tailored to a specific range of output devices without changing the content itself.