title: Csslint: Background image was used multiple times
body: <p>I have this in my css:</p>
  
  <pre><code>@media screen and (max-width:1200px) {
  #cssmenu {
    background:url(/public/system/assets/img/profile.png) no-repeat , url(/public/system/assets/img/bgprofile.jpg) repeat-x;
    width: 100%;
  }
  }    
  
  @media screen and (max-width:970px) {
  #cssmenu {
    background:url(/public/system/assets/img/profile.png) no-repeat , url(/public/system/assets/img/bgprofile.jpg) repeat-x;
    width: 150px;
  }
  }
  </code></pre>
  
  <p>I get an error with csslint task:</p>
  
  <pre><code>Background image '/public/system/assets/img/bgprofile.jpg' was used multiple times, first declared at line 753, col 3. Every background-image should be unique. Use a common class for e.g. sprites. (duplicate-background-images)
  </code></pre>
  
  <p>Is there a way to declare these images so that I don't get this error?</p>
  
  <p>Edit (another case):</p>
  
  <pre><code>.linkmycars
  {
  background:url('/public/system/assets/img/sub.png') no-repeat right 20px, url('/public/system/assets/img/bglinkcars.png') repeat-x #ececec;
  }
  .addcars
   {
   background:url('/public/system/assets/img/add.png') no-repeat right 17px,  url('/public/system/assets/img/bglinkcars.png') repeat-x #ececec;
   }
  </code></pre>
  
  <p>And I get this error: [L651:C1]
  Background image '/public/system/assets/img/bglinkcars.png' was used multiple times, first declared at line 628, col 1. Every background-image should be unique. Use a common class for e.g. sprites. (d
  uplicate-background-images)</p>