A CodePen by Tim Pietrusky. Detect Safari 6+ - With 2/3 dirt and 1/3 feature detection.

script.js

/**
  Detect Safari 6+
  
  With 2/3 dirt and 1/3 feature detection.

  CSS filter are implemented in Safari 6+
  http://caniuse.com/css-filters 
  
  Warning: userAgent stuff is bad.
  But it should work in most of the cases. 
  Use at your own risk >:D
  
  # 2013 by Tim Pietrusky
  # timpietrusky.com
**/

var isSafari6 = 
    !!navigator.userAgent.match(/safari/i) && 
    !navigator.userAgent.match(/chrome/i) && 
    typeof document.body.style.webkitFilter !== "undefined";

document.body.innerHTML = isSafari6 ? 'this is Safari 6+' : 'this is NOT Safari 6+'; 

document.body.className = isSafari6 ? 'isSafari6' : 'not';

style.scss

@import "compass";
@import url(http://fonts.googleapis.com/css?family=Trocchi);

body {
  margin:1em 0;
  font: 700 3.5em 'Trocchi' sans-serif;
  letter-spacing:.075em;
  color: #fff;
  text-align:center;
  
  &.isSafari6 {
    background:#3d9d34;
  }
  
  &.not {
    background:#bf4440;
  }
}