#oscon: Wikipedia use of data URIs (not files) to embed images in CSS reduced size ~27%, requests 35 to 1. Also: embedding images using CSS 'background-image' and Base64 data URIs all in one stylesheet apparently enables gzip to effectively perform compression across multiple images. For backward compatibility with browsers that don't support data URIs in CSS, each 'background-image' is followed by a fallback with a url() to the image followed by '!ie' which is apparently a hack that is accepted by IE5,6,7 (which don't support data URIs). Presentation slides will be here: wikitech.wikimedia.org/view/Presentations