The site is freecodecamp.org.
Progressive Enhancements - A strategy of web design that puts the core content (HTML) first and then progressively adds more rigorous layers of presentation such as CSS. They are needed because they allow everyone to have access to the core content while seeing only the extra styles as their device can handle. This means that the information on the website isn't locked away from people with older devices. This information came from freecodecamp.org.
The sites home page does validate.
There were 26 errors on the site's homepage. Almost all of these were CSS errors, only two being errors with the HTML. The CSS errors were mostly with certain values not being allowed, such as an animation-delay value of 0 not being a real animation-delay value. The actual HTML errors were an attribute href not being allowed on a script element and a stray style element not being allowed as a child of div.
I'd give the site's design an 8. I'm not a huge fan of the colors they chose or the amount of "Get started (it's free)" buttons, but overall it gets their point across and doesn't look too bad.
I'd give the site's usability a 10/10. I haven't found any links or buttons that don't work and I really like how when you use the search bar it puts the results in a new tab instead of taking you off of the page you were on to look at the results.
Yes, I'd say it does meet its purpose.