The Internet Archive's Wayback Machine has extensions for Safari and Chrome, and add-ons for Firefox and Edge, as well as apps for iOS and Android mobile devices, that will allow you to easily save a webpage in the Internet Archive for later reference, as well as some other nice features, with the click of a button. Saved pages don't appear in the Archive immediately, but are placed in the queue for being saved, and that's nice when I come across something online - such as a news article or controversial post on a website - that might be removed later. It will save the page as it was at the time that you clicked the button, so if they later change it or remove the page, you will still have a URL to refer to.
The Internet Archive has been down for the past few days due to a massive DDOS attack, probably combined with a hack.