title: event.returnValue = false of an event
body: <p>I am working on a scrollbar in Javascript. All works fine except for one problem. I notice that while dragging the scrollbar, if I move the mouse over the context that is being scrolled, the content gets selected. I don't want that to happen, so I used the <code>preventDefault</code> method from the event object, which worked perfectly for IE9 and the other modern browsers. But on IE7 and IE8, the problem persists. I did some searches and found that I should set the <code>returnValue</code> parameter of the event object to false. But the problem still persists. Also, if I write <code>alert(window.event.returnValue)</code> it pops up <code>undefined</code>. </p>
  
  <pre class="lang-js prettyprint-override"><code>scrollbar.onmousedown = function (event) {
      if (typeof event == 'undefined') event = window.event;
      if (typeof event.preventDefault != 'undefined') event.preventDefault();
      event.returnValue = false;
      // do some stuff
  }
  </code></pre>
  
  <p>What am I doing wrong?</p>