title: CSS image stripe hover effect not working with jQuery
body: <p>The title might be a little bit confusing. Let me explain my problem:
  I am using CSS image stripes for social buttons. 
  Here is a quick example: </p>
  
  <pre><code>.appnet {
       display:block;
       width:64px;
       height:64px;
       background: url('http://yanlu.de/files/images/SocialButtons.svg') no-repeat;
       background-position:-256px 0;
       margin-right: 10px;
       margin-left: 10px;
  }
  .appnet:hover {
       background-position:-256px -64px;
  }
  .appnet:active {
       background-position:-256px -128px;
  }
  </code></pre>
  
  <p>Now there is my jQuery part:</p>
  
  <pre><code>$('.appnet').css('background-position','-256px -192px');
  </code></pre>
  
  <p>Now, while hovering the button there is no change of the image stripe. Why?</p>