Many large websites are currently down due to a major CDN issue that is used by many large websites. The issue appears to be rooted at the Fastly CDN network.
Websites currently experiencing issues include Amazon, Reddit, and The New York Times.
A CDN is a content delivery network that stores data in regional servers, allowing websites to serve content faster. Faillures are rare, but when they do happen, they have wide-reaching implications as we are seeing happen right now.
For now, end-users will just have to wait for the upstream issues to be resolved and the sites will gradually come back online automatically.