With CSS3 the W3C has introduced a new goodie for design on the web: Media Queries. Until then stylesheets could only be called conditionally by using media types like "print" or "screen". Media Queries extends this to being able to use certain properties as a controlling mechanism if to load a style or not.

You could specify that a stylesheet is only loaded if the browser window has a maximum width of 800px. To do so, you simply extend the value of the media-attribute by the desired attribute and value when inserting the stylesheet. To get our example to work we need to use the following HTML-Code: