Enough knowledge of Hyper Text Markup Language or HTML. One should have proper knowledge of HTML tags and attributes.
CSS for styling a page. HTML without CSS is useless. One should know how to use CSS properly.
Database management and back-end. Back-end is another important part of web development. There are many database programs like MongoDB. One should also have proper knowledge of scripting languages like NodeJS, PHP, Python etc.
Proper knowledge of front-end frameworks, most notably Angular.