LiveReload guard allows to automatically reload your browser when 'view' files are modified.
Modernizr adds classes to the <html> element which allow you to target specific browser functionality in your stylesheet. You don't actually need to write any Javascript to use it.
Scriptaculous, MooTools, jQuery and much more: all you need to develop modern web interfaces and add new features to your website.
Over the last year we’ve been observing what’s happening with the CSS-based web-development, and we collected most useful CSS-techniques we’ve stumbled upon
You don’t have to write the same CSS-code or (X)HTML-Markup over and over again.
Internet Explorer 7 — Hacks und Neuerungen
The primary goal here is to have a set of rules that can be applied during the development phase of a new layout. These rules’ aim is to visually highlight problems in the markup.