title: Background-Position animation issue in Firefox and IE
body: <p>I am a designer turning developer, working on learning parallax. I made this test, and it works great on Chrome, but not in FireFox or IE. Any suggestions?</p>
  
  <p>I am using ScrollMagic, which is built on GSAP.</p>
  
  <p>Here is my script</p>
  
  <pre><code>$(document).ready(function($) {
      // build tween
      var tween = TweenMax.fromTo("#clouds2", 5, 
              {"background-position": "50% 0px"},
              {"background-position": "50% 2500px"}
          );
  
      // build scene
      var scene = new ScrollScene({triggerElement: "#container", duration: 3000})
                      .setTween(tween)
                      .addTo(controller);
  
      // show indicators (requires debug extension)
      scene.addIndicators();
  });
  </code></pre>
  
  <p><a href="http://joeyellisdesign.com/testingspace/parallaxtest/test/" rel="nofollow">http://joeyellisdesign.com/testingspace/parallaxtest/test/</a> </p>