UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.
CSS Peeper - Smart CSS viewer tailored for Designers.
draw.io - Online diagramming application
Purgecss - Easily remove unused CSS
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
Tailwind CSS - A utility-first CSS framework for rapidly building custom user interfaces.