These are not error and also it is generated by you customize but by our theme.
Validation Output: 3 Errors
Line 12, Column 77: Attribute xmlns:og not allowed here.
<html dir="ltr" lang="en-US" xmlns:og="http://opengraphprotocol.org/schema/">
This is through opengraph you use. This is not a problem
Line 361, Column 108: Bad value generator for attribute rel on element a: Keyword generator is not registered.
…"Maintained By AMDS Solutions" rel="generator">Maintained By AMDS Solutions</a>
This by rel="generator" and it's not an error.
Line 363, Column 98: Bad value designer for attribute rel on element a: Keyword designer is not registered.
…ws8.org/" title="Theme By Nick And Mac" rel="designer">Theme By: Nick & Mac</a>
This also rel="designer" and it's not an error.
All these errors are shortcomings in the Validator itself. I don't see any meaningful validation errors being reported. HTML 5 and it's validator are still in the "experimental" stage.
Note: Not Allowed
Also, you are not allowed to change the Theme By: Catch Themes to Theme By: Nick And Mac. This is a direct violation of the theme's copyright. You can't just take something made by somebody else and claim you did it yourself.
Please change back.