Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions
Little Widgets - HTML, CSS Framework with beautifully designed website widgets, popups, and forms.
Element UI - A Desktop UI Library. Element, a Vue 2.0 based component library for developers, designers and product managers.
Remindee - Capture & convert more attendees for live and online events.
Responsive Grid System - Spectacularly Easy Responsive Design
Pop Up Maker by Landingi - Stop losing visitors and start converting