Detect CSS3 Support in Browsers with JavaScript http://net.tutsplus.com/tutorials/html-css-techniques/quick-tip-detect-css-support-in-browsers-with-javascript/

css3_support_detect.js

var supports = (function() {
  var div = document.createElement('div'),
      vendors = 'Khtml Ms O Moz Webkit'.split(' '),
      len = vendors.length;

  return function(prop) {
    if ( prop in div.style ) return true;

    prop = prop.replace(/^[a-z]/, function(val) {
      return val.toUpperCase();
    });

    while(len--) {
      if ( vendors[len] + prop in div.style ) {
        // browser supports box-shadow. Do what you need.
        // Or use a bang (!) to test if the browser doesn't.
        return true;
      }
    }
    return false;
  };
})();