I take a lot of screen shots of the various device breakpoints for responsive design and it takes a while to prepare them. This tools allows me to get what I need quickly, and hopefully it can be helpful for showing your more visual clients what you mean by responsive design when a suite of products isn't at the ready.
a lightweight structured data publishing framework that lets you create web pages with support for sorting, filtering, and rich visualizations by writing only HTML and optionally some CSS and Javascript code.
"Yet Another Multicolumn Layout" (kurz YAML) ist ein (X)HTML/CSS Framework zur Erstellung moderner und flexibler Layouts auf Grundlage von float-Umgebungen.