Some of the most important skills for a web developer are:
HTML defines the structure of a web page whereas CSS is used to modify and enhance that structure by adding styling. You must have a good grip on these two languages to design a good front-end.
A good developer must have a solid grasp of the web protocols HTTP and HTTPS and how they work, as well as of of how clients and servers communicate. Working knowledge of Secure Shell Protocol (SSL), used to encrypt the data between servers and clients, is also very helpful.
A good developer will often want to use a framework to make web development faster and easier. Some popular frameworks include:
Vue.js for frontend and
Ruby on Rails,
Django for back-end.
To write the server side of your website, you need to have a sound grip of some back-end technology. The most popular ones are
Web devs will often need the command line to install packages and build web applications.