html prototyping

InstaCSS: CSS Documentation Search

Animate.css: Plug-and-play CSS animation styleshee ...

{placekitten}

Placehold.it: Simple image placeholders

lorempixum: Placeholder images for every case
Wirify: Create wireframes from web pages

CSS Sticky Notes

CSS Tooltips and Speech Bubbles

quplo: HTML Prototyping

Google Chrome Extensions for web developers

HTML Wireframe Tool

UKI: Simple UI Kit for complex web apps

Easy front-end framework
Zen Coding: Plugins for HTML and CSS hi-speed codi ...

StaticMatic: Static HTML building framework