The home page did not validate.
Nope the second page how to learn linux terminal as a beginner didn't validate either.
I would rate it an 8. I don't see any glaring issues with it. It's clean and well ordered.
The site is very user friendly I'd give it an 9. The site is a free education site with a plethora of topics to examine. My instant gratification monkey really wanted to stay and dig in. Fortunately I have him pretty well subdued currently and I was able to resume my school work fairly easily.
I would say that it meets it's purpose quite well.