& ldquo; The frameborder attribute of the iframe element is deprecated. Use CSS instead. & Rdquo;


I'm trying to validate my website with the W3C validator but it doesn't work. I have a YouTube iframe and this is the error:

The frameborder attribute on the iframe element is obsolete. Use CSS instead.

Screenshot: http://i.stack.imgur.com/VCiJV.png

And this is my index.html (cropped):

<!-- Video -->
<div class="video-container box-size">
  <iframe width="700" height="312" src="http://www.youtube.com/embed/OfUPsnAtZMI" frameborder="0" allowfullscreen></iframe>

How can I correct it?

As they state themselves "The frameborder attribute is not supported in HTML5. Use CSS instead."

The equivalent of frameborder in css is border: 0px;. Add it to your iframe in css.