title: z-index issue with background image and image parent tag
body: <p>i've some problem with the z-index property:
  This is the code:</p>
  
  <pre><code>&lt;div id="sidebarCont"&gt;
  &lt;div id="avatarCont" class="mask"&gt;
      &lt;img id="" class="" src="img.jpg" alt=""/&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p></p>
  
  <p>and the css:</p>
  
  <pre><code>#avatarCont{
  overflow:hidden;
  height:160px;
  width:160px;
  margin:0px auto;
  background:url('../img/mask.png') no-repeat;
  position:relative;
  z-index:70;
  </code></pre>
  
  <p>}</p>
  
  <pre><code>#avatarCont img{
  position:absolute;
  top:0px;
  left:0px;
  z-index:50;
  </code></pre>
  
  <p>}</p>
  
  <p>i whant to have a mask on the image, someone have ideas to solve the problem?</p>