-moz-user-select:none的表现变得和-moz-user-select:-moz-none相同,也就是和其他浏览器实现了统一Previously, when you set the none keyword to the -moz-user-select property, the text of on the element and sub-elements became unselectable, even if one of those sub-elements had -moz-user-select:text. Starting with Firefox 21, none behaves like -moz-none and other browsers, so selection can be re-enabled on sub-elements using -moz-user-select:text.
对table的cols和layout属性的支持Firefox no longer accepts the cols and layout properties on the table elements. No other browsers support these obscure properties.
scrollWidth和scrollHeight不再受overflow:visible的影响The scrollWidth and scrollHeight properties might have wrong values when CSS overflow:visible was set on the element. This behavior has been fixed to match the values as if overflow:hidden is set.
window不再接受自定义的索引属性Setting indexed expandos (custom properties which have number as the property name) on the window object is no longer allowed. Your code like window[2] = "myString" will be ignored from now on.
window对象上的索引属性变的可枚举Previously, iframes in the DOM were not enumerable on the window object. This behavior has been changed to comply with the spec, which means they are now returned with Object.keys(window). This is important to note for things like global leak detection, since appending iframes to the document will modify the enumerable keys on the window object.
XMLHttpRequest.setRequestHeader方法的实现遵循了当前规范Previously, if the same headers were repeatedly set with XMLHttpRequest.setRequestHeader, the last-specified value was used. This behavior has been changed to comply with the spec, so those values will be properly combined.
formMethod和formEnctype的默认值成为一个空字符串The HTML5 spec of the formMethod and formEnctype properties has been updated to have the empty string as default value. Firefox followed the change.
如果传递多条规则,CSSStyleSheet.insertRule方法会报错If multiple rules was passed to the CSSStyleSheet.insertRule method, only the first rule was inserted into the stylesheet. Instead, Firefox now throws an exception SYNTAX_ERR like other browsers.
NodeIterator和TreeWalker上删除掉expandEntityReferences属性The expandEntityReferences property, which returned a flag indicating whether or not the children of entity reference nodes were visible to the object, has been removed from the NodeIterator and TreeWalker objects, as it never made much sense.
CSSKeyframesRule.insertRule方法被改名为appendRuleOne of the methods of the CSSKeyframesRule interface, insertRule has been renamed to appendRule to match a spec change.
HTMLInputElement.inputmode现在默认被禁用HTMLInputElement's inputmode API, which has been implemented since Firefox 17, is now disabled by default because the spec is still unstable. You have to enable the dom.forms.inputmode pref or use the Aurora channel to try out this feature. Note that this API will be renamed inputMode (capitalized M) in Firefox 22.
The support of ECMAScript for XML (E4X), deprecated and disabled since Firefox 17, has finally been dropped. You can no longer use the feature regardless of the hidden preference.
parseInt把以0开头的字符串当成十进制数字解析,而不是以前的八进制The parseInt method implementation has been updated to conform to the ECMAScript 5 spec, and it now parses leading-zero strings as decimal, not octal. Therefore, parseInt("042") will return 42 instead of 34. If you'd like to parse strings as octal, specify the radix like parseInt(str, 8).
String.localeCompare在无参情况下的表现,以符合ES5规范The String.localeCompare method implementation has been updated to conform to the latest ECMAScript 5 spec. If no argument is passed, the method takes the "undefined" string as the argument.
Unimplemented SVG features have been removed instead of just returning the NOT_IMPLEMENTED errors. These features include the viewport and currentView properties of SVGSVGElement.
mozAudioContext属性脱前缀The mozAudioContext implementation has been unprefixed. It's still disabled by default, though. To try out this feature, change the value of the media.webaudio.enabled pref to true.
Content Security Policy (CSP) 1.0 spec has been implemented. The existing parser will be used when a policy is served via the X-Content-Security-Policy header, and the new parser that follows the 1.0 spec will be used when a policy is served via the officially spec'd Content-Security-Policy header. Consult the latest spec if you'd like to implement CSP on your site. The documents on MDN will be updated sometime soon.