jQuery UI 1.10 Upgrade Guide（升级指南）中指出

jQuery UI 1.10 Removed support for IE6

IE6 usage has dropped to a low enough point that jQuery UI no longer finds it necessary to support. As of 1.10.0, some portions of jQuery UI may not work properly in IE6. If you need to continue to support IE6, use the latest jQuery UI 1.9 release.

原文：http://jqueryui.com/upgrade-guide/1.10/#removed-support-for-ie6

jQuery UI 1.11 Discontinued IE7 Support

As of this release we are no longer accepting bug reports for IE7 issues. We have also removed IE7 from our testing infrastructure. The IE7 workarounds are still present in the code, but we will remove them for jQuery UI 1.12.

http://jqueryui.com/upgrade-guide/1.11/#discontinued-ie7-support

也就是，只有jQuery UI 1.9及以下版本才支持IE6

jQuery UI 1.10不再支持IE6，jQuery UI 1.11不再支持IE7