Ask browser users, and they'll tell you the overwhelming reason why they can't upgrade to a more modern, standards-compliant browser is because their work won't let them. Ask IT departments why this is the case and they'll point to the six- to seven-figure costs of upgrading turn-of-the-century Intranets written to work in, and only in, Internet Explorer 6. Google have provided a way for websites to opt out of IE6 (and even IE7) support without requiring enterprise-wide, Intranet-breaking browser upgrades.