WordPress oEmbed iframe video W3C Validation

The frameborder, webkitallowfullscreen and mozallowfullscreen are obsolete or invalid iframe attributes and should be removed from youtube and vimeo video oEmbeds. WordPress automatically adds these attributes with video oembeds from popular sites like vimeo and youtube.

Use CSS to remove any border styling from iframes.

You can use this function in your WordPress theme’s functions.php file to ensure your iframe code for vimeo or youtube video oEmbeds are valid.