title: css image background position dynamic
body: <p>I was working in a webapp (<strong>html</strong> / <strong>css</strong>) and I was asking myself if it's possible with css get what I've asked in the title. </p>
  
  <p>I have this html:</p>
  
  <pre><code>&lt;input type="text" class="custom-bg"&gt;
  </code></pre>
  
  <p>And this css:</p>
  
  <pre><code>.custom-bg { 
    background: url(icons.png) right -4579px no-repeat; 
    background-size: 39px 39px; //Size of the icon
  }
  </code></pre>
  
  <p>My input is not always the same size, it may change if you resize the browser.<br>
  I want to put that icon (it's a down-arrow) in the right top corner, that's why I have <code>right</code> in the <code>background</code> property. </p>
  
  <p>I want something like position: right <strong>5%</strong> instead of a fixed position or value (number). </p>
  
  <p>Is possible? (I mean the css-way, no js) It's an big webapp and there are some classes I can't touch.</p>
  
  <p>Thanks</p>