Bootstrap is the most popular HTML, CSS, and JS framework for developing responsive, mobile first projects on the web.
Vex Alert 2.2.1
Vex is a modern dialog library which is highly configurable, easily stylable, and gets out of the way. You'll love vex because it's tiny (6kb minified), has a clear and simple API, works on mobile devices, and can be customized to match your style in seconds.
Custom Built and Crisp Icon Fonts, Done Right