Validation Error - Social Buttons

I did the Markup Validator, and it quickly replied that and error was found while checking this document as html5. There were 15 errors and 5 warnings for my site: 
http://www.shepardhavenlaw.com/

Then i did the Link Checker, this took a little longer and showed some errors, but they were different and much less alarming. I guess my question is, do these errors devalue my site? Most of the errors have to do with the favicon and the social media buttons.