Hi, I am Terry Avery, a website coder and designer and computer specialist, and support you by way of linking to your site from mine.
Every page on my site links to yours with a validation option for both HTML and CSS.
I have recently reworked my entire website, and need to update the links per page, and cannot do that until the URL validation is working.

It appears you have a connection error to validator.nu when checking my HTML 5 markup by URL, where just a couple of days ago it was working fine.
When the markup is uploaded, or direct input, it works fine, just not by URL, which is the means I use to show support for you and get people to go to your site.

I checked it directly at validator.nu, and it works fine there.

Error as shown on your site:

Error External Checker not available
Checking the Document Type of this document requires the help of an external tool which was either not enabled in this validator, or is currently unavailable. Check in the validator's system configuration that HTML5 Validator is enabled and functional.
The error encountered was: 500 Can't connect to localhost:8888 (connect: Connection refused)

If there is any other ways I can be of help to you, please let me know.
~Terry Avery

      T Avery Enterprises
Computers, Networking, Websites, Graphics, Photography & Video