PrettyCSS is described as 'Build your website interface using a responsive CSS framework with various components and with integrated dynamic functionalities' and is a CSS Framework in the Development category. There are more than 50 alternatives to PrettyCSS for a variety of platforms, including Online / Web-based, Self-Hosted solutions, Mac, Windows and Linux. The best alternative is Bootstrap, which is both free and Open Source. Other great apps like PrettyCSS are Bulma (Free, Open Source), Materialize (Free, Open Source), UIkit (Free, Open Source) and Semantic UI (Free, Open Source).
A unified, HTML5-based user interface system for all popular mobile device platforms, built on the rock-solid jQuery and jQuery UI foundation. Its lightweight code is built with progressive enhancement, and has a flexible, easily themeable design.