Web application front-end developers needs to have an in-depth knowledge of HTML 5 and CSS3. The modern web delivery becomes much easier if CSS frameworks like Twitter Bootstrap, Foundation, Skelton, Materialize Helium, WebUI, Karma CSS or Pure.css are applied. The CSS becomes much more maintainable and reusable if CSS pre-processor like Sass, LESS, or Stylus are brought into practice. More recently the front end developers also are expected to be an expert in JavaScript core and its platforms like Angular Js, Angular, React, Vue Js, jQuery, Knockout to name a few.