With a title like that, you just know this is going to be fun. (No, seriously.) The user agent string is one of those wonderfully eclectic things, a balance of modernity and antiquity. Except mostly skewed toward antiquity. It’s grown, piece by piece, over the years; because everyone has their own special way of parsing it, it’s a notoriously sensitive beast. Adding to it is relatively simple, but
![Final User Agent String for Firefox 4 – Mozilla Hacks - the Web developer blog](https://cdn-ak-scissors.b.st-hatena.com/image/square/8f043099b608abf8384b24171faa177d3698e62e/height=288;version=1;width=512/https%3A%2F%2Fhacks.mozilla.org%2Fwp-content%2Fthemes%2FHax%2Fimg%2Fhacks-meta-image.jpg)