A Cross-Browser Responsive Design Helper: CSS Browser Selector +
It forces no hacks but promotes compliant code and also provides an alternative method of mediaqueries for older browsers.
The details it can detect include browser, browser version, platform, platform version, device, device version, min-width/max-width screen detection and orientation screen detection (landscape or portrait).
A sample usage would look like:
<html lang="pt-br" class="webkit chrome chrome21 win win8 js orientation_landscape minw_980 maxw_1199"> that is pretty self-explanatory.