But, never fear! It's been archived! Take another look at that banner and you'll see a link to a version of the EPA's website as it existed on January 19, 2016. There's also an EPA Web Archive that can be used to search information no longer available on EPA.gov.
Why is this a big deal? Has the EPA website really changed that much? Well, here's an example.
Search the current EPA.gov pages for the term "climate change" there are 5,670 results. Search the January 19, 2016 version and there are 10,600 results. The web archive has 12,500 results. That's a lot of information on climate change that wouldn't be available if not for the web archive and January 19 snapshot.