You can use media queries today
Media queries are already widely used and enjoy a broad level of browser support (Firefox 3.6+, Safari 4+, Chrome 4+, Opera 9.5+, iOS Safari 3.2+, Opera Mobile 10+, Android 2.1+, and Internet Explorer 9+). Furthermore, there are easy to implement (albeit JavaScript based) fixes for common aged browsers such as Internet Explorer versions 6, 7, and 8. If you need to grab the fixes for Internet Explorer versions 6, 7, and 8 now, you'll need to look at Chapter 9, Solving Cross-browser Responsive Challenges. In short, there's no good reason why we can't get using media queries today!
Note
Specifications at the W3C go through a ratification process (if you have a spare day, knock yourself out with the official explanation of the process at http://www.w3.org/2005/10/Process-20051014/tr), from Working Draft (WD ), to Candidate Recommendation (CR ), to Proposed Recommendation (PR ) before finally arriving, many years later, at W3C Recommendation (REC ). So modules at a greater maturity level than others are generally safer to use. For example, CSS Transforms Module Level 3 (http://www.w3.org/TR/css3-3d-transforms/) has been at WD status since March 2009 and browser support for it is far scanter than CR modules such as media queries.