Save a couple of bytes here and there, and you may save a whole packet; saving a packet when your packet count is small can make a big difference in download times, since TCP slow start means lots of round trips in the beginning of a connection. Also, less data transfered is good for people with data caps, and lets your server do less work. That said, you'll probably get more out of making sure your images are optimized, and apparently changing from sprites to fonts (if your target audience supports it).