W3C Markup Validation Service and CSS Validation Service May 12, 2014 Online Tools Make sure your codes and styles validate across the board. That means they have to meet the strict standards set by the W3C Organization and pass a variety of validations for CSS and XHTML. These are two online validation services below: HTML CSS Post navigation Previous Previous post: Compress your JavaScript and CSS filesNext Next post: Powerful Social Share Buttons Plugin for WordPress