Today I found this
jQuery 2.0 Drops Support for IE6, 7 and 8
interesting article on the sitepoint.com site.
Another reason for upgrading your browser.In a surprise announcement on the jQuery blog the team has decided that jQuery 1.9 will be the last edition to support legacy editions of Internet Explorer. jQuery 2.0 — planned for release in 2013 — will no longer support IE6, 7 and 8.
In essence, jQuery 2.0 will be a leaner, faster library without old IE bloat such as DOM selection routines, different event models and HTML5 shims.
Related Sitepoint articles:
Browser Trends July 2012: IE9 Strikes Back
What’s New in Chrome 20