Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions
Purecss - A set of small, responsive CSS modules that you can use in every web project.
Vuetify - Material Component Framework for VueJS 2
Materialize CSS - A modern responsive front-end framework based on Material Design
HTML5 Boilerplate - A rock-solid default for HTML5 awesome.
HTML5 - 5th major revision of the core language of the World Wide Web