For many beginners, w3schools has structured tutorials and playgrounds that offer a decent learning experience. The certificates on w3schools, however, are just random certificates on a random internet site—i.e., they’re basically worthless and not worth paying money for. In what way do you believe that it is “not working”?
Downloading offline versions of w3schools or devdocs or something similar? The code is valid and when i copy it into a local file i see the expected results. Covering popular subjects like html, css,.
However, it would be a mistake to continue your education. I usually just use w3schools as a quick reference. Html a target attribute w3schools offers free online tutorials, references and exercises in all the major languages of the web. They do have some comprehensive stuff but it is not enough but hey, i use it as additional resource besides mdn.