from MDN Web Docs
Learning some HTML, CSS, and JavaScript is useful if you want to become a web developer, but your knowledge needs to go further than just using the technologies — you need to use them responsibly so that you maximize the audience for your websites and don't lock anyone out of using them. To achieve this, you need to adhere to general best practices (which are demonstrated throughout the HTML, CSS, and JavaScript topics), do cross browser testing, and consider accessibility from the start. In this module we'll cover the latter in detail.