title: Fallback img src for images from external sites
body: <p>I need to display images from other sites and have a view model with a <code>imgsrc</code> property that references an image URL. Then I have the following HTML binding:</p>
  
  <pre><code>&lt;img data-bind="attr: { src : imgsrc }" /&gt;
  </code></pre>
  
  <p>The problem is that with a bound image being external, I could get a 404 or 500 response if the external site is having issues; therefore, I want to display a fallback image in case we can't load the image.</p>
  
  <p>How can this be achieved using KnockoutJS?</p>