title: Highcharts: cutom tooltip (useHTML: true) z-index issue over resetZoomButton
body: <p>My issue is as following:</p>
  
  <p>I've created a custom tooltip with formatter callback function and had set useHTML attribute to be true.
  The problem with useHTML is that it is not respecting z-indexing, and the result is that whenever i zoom in the chart (when the reset zoom button actually appears), the reset button's text gets covered by the tooltip's text.</p>
  
  <pre><code>   tooltip: {
          useHTML: true,
          followPointer: true,
          formatter: function() {
              return '&lt;b&gt;sSsSsSsSsSsSsssssssssssssssssssssS&lt;br/&gt;sdsdsddddddddddddssd&lt;/b&gt;';
          }
     }
  </code></pre>
  
  <p>check this fiddle:  <a href="http://jsfiddle.net/sahar_rehani/R5Ep4/" rel="nofollow">http://jsfiddle.net/sahar_rehani/R5Ep4/</a></p>
  
  <p>try zooming in and then get the tooltip closest to the reset zoom button :)
  please help!!!</p>