front-end performance is more critical then back-end performance. Front-end performance is also a critical priority for Zen. That’s why Zen 5’s markup and CSS footprint is so small. After turning on Sass production-mode compilation, the total CSS is only 14k; this includes the layout, vertical rhythm support, print styles, all the appropriate vender prefixes (like -o and -khtml), CSS3-prettified tab styling and the 3 menu images that are included via Data URIs into the CSS. Zen includes no images and only 2 JavaScripts (which are only loaded conditionally by IE8 and lower,