How to use JavaScript to change div backgroundColor

The HTML below:

<div id="category">

  <div class="content">
     <h2>some title here</h2>
      <p>some content here</p>
  </div>

  <div class="content">
     <h2>some title here</h2>
      <p>some content here</p>
  </div>

  <div class="content">
     <h2>some title here</h2>
      <p>some content here</p>
  </div>

</div>

When mouseover the content of div then it's backgroundColor and the h2 (inside this div) backgroundColor change (just like the CSS: hover)

I know this can use CSS (: hover) to do this in modern browser but IE6 doesn't work.

How to use JavaScript (not jQuery or other JS framework) to do this?

Edit:how to change the h2 backgroundColor too