Knowledge of markup languages
Being new to your career as a web developer, you should learn about HTML and CSS. These are the basic languages that every web developer should know. HTML is used to create a structure of a website and to add tags to make it interactive while CSS helps you to make a web application interactive.
This skill is mandatory as the market requirements are based on accessing mobile devices than that of websites. Therefore, you should design a web application that could be supportable to the mobile devices as well. Companies that provide React JS development services look for this skill in a React JS developer as responsive designs are in demand.
Cross Browser Development
You should how to make your website compatible to be accessed on any web browser like Mozilla Firefox or Google Chrome. You can create a website that could run on a platform like an internet explorer; what if a user wants to access it on Google Chrome? You have to make sure that you are addressing browser compatibility also when developing a website.