Websites disappearing is the reason why the Wayback Machine exists. If there's a site you love check to see if the Machine has a version of it... and if not (or if you want to add the current version), they have a "Save Page Now" option right on the homepage. Use it! Your future self will thank you!

And I completely and totally agree with unity. I'm SO lucky that I had junior high teachers who forced us to learn how to use databases, libraries and physical books, archives with physical primary source stuff, etc. in addition to the internet. Being able to do all of that has given me the key to so much more knowledge than Google and other search engines have to offer... and it's a shame that most other people my age can't access it!