My bet is that it's an issue with the CDN. It's not uncommon for content platforms and ecommerce platforms to utilize content delivery networks to serve static assets such as CSS, Javascript, and images. When you hit assets.whatever.com, it's actually going to serve that from a machine that is physically closer in location to you. This typically results in a faster experience, but if a region of the CDN is down and there isn't a good failover, you're going to see something like what's going on with nin.com.
Those of you who are seeing a messed up nin.com - what happens when you visit the following URLs:
https://de1daada60dfbf786b6e47a9-the....css?ver=5.2.4
https://de1daada60dfbf786b6e47a9-the....css?ver=1.5.0