w3c validation - "The frameborder attribute on the iframe element is obsolete. Use CSS instead." -

w3c validation - "The frameborder attribute on the iframe element is obsolete. Use CSS instead." -

i'm trying validate website w3c validator doesn't work. have youtube iframe , error:

the frameborder attribute on iframe element obsolete. utilize css instead.

screenshot: http://i.stack.imgur.com/vcijv.png

and 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> </div>

how can right it?

as state "the frameborder attribute not supported in html5. utilize css instead."

the equivalent of frameborder in css border: 0px;. add together iframe in css.

iframe w3c-validation