According to the latest figures from Microsoft a staggering 2/3 of all computers are running out of date browsers.
That means you’re not getting the latest security patches and you’re at risk of not seeing the layout exactly the way the designer intended.
Purely self-interestedly, it would also make our job at Reverse Delta massively easier if we knew everyone had up-to-date browsers! We spend a lot of time dealing with the quirks of all the different browsers and making sure everything is backward compatible (if half of that problem just disappeared, we could all take longer lunches and keep more of our hair!).
Naturally Microsoft would like you to install their latest browser (which admittedly is very good) but do yourself a favour and make sure you’re using the latest version of your browser of choice.