Jquery是继prototype之后又一个优秀的Javascrīpt框架。它是轻量级的js库(压缩后只有21k) ，它兼容CSS3，还兼容各种浏览器 （IE 6.0+, FF 1.5+, Safari 2.0+, Opera 9.0+）。jQuery使用户能更方便地处理HTML documents、events、实现动画效果，并且方便地为网站提供AJAX交互。jQuery还有一个比较大的优势是，它的文档说明很全，而且各种应用也说得很详细，同时还有许多成熟的插件可供选择。jQuery能够使用户的html页保持代码和html内容分离，也就是说，不用再在html里面插入一堆js来调用命令了，只需定义id即可。
jQuery 1.5.2更新日志：
#6158 Fixed replaceWith from throwing errors on non existent elements.
#7340 We now use a single capturing handler to simulate bubbling focusin/focusout event on non-IE browsers. Allows native DOM methods to fire events other than the currently active one back into jQuery.
#8353 Reverted. Adds a catch block in resolveWith so that the finally block gets executed in IE7 and IE6. Fixes #8438 – an issue where the full functions stack wasn’t visible when debugging in Google Chrome.
#8380 Make it so that $(‘:text’) matches <input> as ‘type=text’ is the implied default.
#8421 Makes sure resolveWith can be called with only one parameter.
#8423 Never set X-Requested-With header automagically for cross-domain requests. Fixes an issue where all cross-domain ajax requests are pre-flighted and require extra additional options.
#8456 Fixed an issue where trigger(‘mouseover’) was no longer triggering mouseenter. We make sure parent is not null before crawling into its lap, so mouseenter is triggered on a mouseover event.
#8509 Makes URL regexp less overzealous and ensures it recognizes URL schemes which do not contain a conformant hierarchical structure (as per section 2.1.2 of http://www.ietf.org/rfc/rfc2718.txt). Also adds about: and adobe air’s app: and app-storage: to the list of local protocols and provides a failover in case document.location is illformed.
#8536 Introduced submodules to the jQuery repository on GitHub.
#8381 Fixed .is(“div”) to work on disconnected nodes in IE 9.
#8316 Fixed .offset() setter on fixed elements in WebKit.
#3333 Fixed incorrect .css(“marginRight”) in WebKit.
#8692 Fixed an issue where the arguments object sometimes ended up with undefined values outside the $.when method.
#8346 Fixed a compatibility issue with jQuery.camelCase() and IE9 prefixes.
#8203 Removed some unnecessary nulling of elements done in the name of an IE memory cleanup.
#8519 Prevent the core makefile from applying minification if nothing in the code has actually changed.
#8587 Fixed the jQuery-git.js cron-job to ensure that it is being regularly updated.
#8635 Corrected an issue with Firefox 3.6 where an issue with getComputedStyle() was resulting in uncaught exceptions.
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