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This document will summarize the level of support for web standards and maturing technologies in popular web browsers. It covers the Internet Explorer, Firefox, and Opera web browsers, with focus on the HTML, CSS, DOM, and ECMAScript technologies.

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Visitors with visual impairments may take advantage of a magnified version or a monochrome version of these documents. In most web browsers, you can select your preferred view by going to the View menu and then Page Style or Style. This mechanism is not supported by Internet Explorer or Safari.

How to interpret these tables

Each row corresponds to a feature of the particular web standard or maturing specification. In the full tables, the browser support for that feature is usually indicated by a single letter: Y (yes), N (no), or I (incomplete support). A question mark (?) means that the support for that feature is currently unknown. The values have been colored for readability. Most feature names in the full tables are links to the official standards definitions.

Some features are listed as a summary of another group of features on the tables. These summary features often show percentages indicating the mean average support for the features in that group. Incomplete (I) support for a feature is calculated as a 50% support. Features with unknown levels of support are ignored. Features that are irrelevant in the summarized context are also ignored, such as the “inherit” values in the individual components of CSS shorthand properties. If more than 5% of the data in the summarized group is unknown, it simply lists a question mark. If all of the summarized features have all or no support, the summary feature simply lists a Y or N, respectively. If there is only one feature summarized and it has an I rating, the summary feature simply lists an I.

Some summary features summarize a feature breakdown that is not written out on these tables but is obvious in the standard's specification, such as a predefined set of possible values for an attribute in HTML. These summary features assume a value for general support and an additional value for each part of the breakdown in order to arrive at the displayed percentage.

The tables on this page and the summary page are in summarized form. Each row is a summary feature of the corresponding group in the full tables. Feature names are links to the corresponding sections of the full tables.

Some feature ratings have explanations associated with them, particularly for those with an “I” rating. The explanations are stored in the title attribute of the table cell or in a mouseover event for user agents supporting ECMAScript, and can usually be accessed by user agents with mouse support by hovering the mouse cursor over the table cell. These rating symbols are marked with an overline.

There are three families of web browsers shown here by default: IE, Firefox, and Opera. IE values are relevant for Microsoft Internet Explorer for Windows, Maxthon, Netscape in “I Trust This Site” or Internet Explorer mode, Avant Browser, AOL Browser, and other programs that use the Trident layout engine. (It should be noted that Internet Explorer for the Macintosh uses a different layout engine.) Firefox values are relevant for corresponding versions of Mozilla Firefox, the Mozilla Application Suite, Seamonkey, Netscape in “I'm Not Sure” or Netscape mode, Camino, Flock, Galeon, Epiphany, and other programs that use the Gecko layout engine. Opera values are relevant for Opera, Dreamweaver on Mac OS X, Adobe Creative Suite 2, and other programs that use the Presto layout engine. For features that are specific to the interface of the browser rather than simply the layout engine, the named web browser is the browser being tested.