Data URIs are one of the best techniques in CSS, allowing developers to avoid referencing external images and instead embed them directly into a stylesheet. The main advantage of this approach is to save HTTP requests.
HTTP requests are a huge performance bottleneck, and the reason techniques such as CSS image sprites have been popular for some time. Basically, if you can avoid requesting an extra file, not only does it save your server the work of looking up the file, but it also saves your user the download time. In fact, HTTP request management is so important, that it is the top issue in the Yahoo Performance Rules.
Data URIs are an excellent way to reduce HTTP requests and speed up your pages, so let’s walk through how to use them in all major browsers.