Anyone with an idea and internet access can create a website and fill it with just about any content they want. As of 2018, there are over 1.8 billion websites in the world, many of which are protected by free speech and anti-censorship laws. Website owners can print anything they want, true or not, without worrying about the consequences.
This post from WhoIsHostingThis posits that the oceans of data and globe-spanning inter-connectivity of the internet make verifying sources easier than ever as well.
In addition to the time-honored practices of using primary sources, identifying their authors, etc., there are additional tools you would normally not think of. Tools like the Grammarly’s Plagiarism Checker, checking out the domain name, publication dates, and cross referencing with your library’s research databases.