Originally posted on: http://geekswithblogs.net/renso/archive/2013/10/31/jquery-2.0-drops-support-for-legacy-ie-ie6-ie7-ie8.aspxjQuery upgrades may not be as reverse compatible as you may think. Starting from version 2 of jQuery, IE6, IE7 and yes also IE8 will no longer be supported. These are now considered legacy browsers. You will need to stop any upgrades to jQuery until your SLA states that IE8 is no longer supported and remain in jQuery 1.9.Some of the reasons for not supporting IE8 and before:- Remove all the code clutter in the jQuery library with code that has to deal with IE browser compatibility issues between IE6, 7 and 8 and the newer IE versions, the latter being more compliant.- IE6 and 7 may have fallen to below 2% generally, that does not mean that that is true for your client base. In the oil and gas industry some clients are years behind and you may have 50% or more of clients remain on IE8 or older for the foreseeable future.- The difference between browser engines has become almost negligible, as it should be. So one of the greatest goals of jQuery to abstract that out for developers is no longer needed, for most part anyway. - CSS3 features like animations basically replace the need for jQuery’s 2.0 animations and effects.If the need is still there to support IE8 or before, but you also want to upgrade, then use conditional comments:<!--[if lt IE 9]> <script src="jQuery-1.9.0.js"></script><![endif]--><!--[if gte IE 9]><!--> <script src="jQuery-2.0.0.js"><</script><!--<![endif]-->
