Glossary Term: W3C Validation
W3C validation means if the tag in a page meets the W3C standard. The most popular W3C validator available online is from "The W3C Markup Validation Services by W3C®. It does not plays a heavy role in search engine optimization. But it does show the site owner cares about the site and pay more attention to meet the common agreed standard. One advantage is that page that meets the W3C standard will most likely be more cross-browser compatible.