title: Why am I getting "event.returnValue is deprecated..." and how can I rectify it?
body: <p>In my web site, when I F12 from the browser, I see in the console (Chrome Dev Tools) the error/warning, "<em>event.returnValue is deprecated. Please use the standard event.preventDefault() instead.</em>"</p>
  
  <p>Yet I search my project for "<em>event.returnValue</em>" and it turns up no instances of that string. </p>
  
  <p>Assuming it is some Microsoft or jQuery-written code that is causing this, should I do something about it, and if so, what?</p>