Web Design & Development Guide

Comparison of layout engines (CSS)

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The following tables compare CSS compatibility and support for a number of layout engines. Please see the individual products' articles for further information. This article is not all-inclusive or necessarily up-to-date. Unless otherwise specified in footnotes, comparisons are based on the stable versions without any add-ons, extensions or external programs.

Engine Nomenclature

• Trident is the layout engine used in Internet Explorer for Windows.
  Tasman is used in Internet Explorer for Macintosh.
  Gecko in all Mozilla software.
  WebCore provides the HTML layout engine for Mac OS X.
  KHTML for KDE.
  Presto for Opera.
  iCab is a browser for the Mac.

Meaning of Values

"Yes" indicates that the current version of the browser fully supports this property when valid values are used. "No" indicates that this property is completely ignored. "Partial" indicates that the property is understood, but that not all values are supported. Supported values are implemented correctly. "Buggy" indicates that the property is understood, but that it is not implemented correctly in all cases. "Dangerous" indicates that the property is understood, but that deleterious behaviour results. Version numbers, where known, are provided to indicate when support for this feature was added. If support was added in a publicly available unofficial release (such as an alpha or beta version), a red background is used. Proprietary properties are not included.

General overview

See the article Cascading Style Sheets for more information on the different versions of CSS. This table doesn't reference CSS2.0, as CSS2.1 was intended to replace it by correcting or removing a few errors and features rejected by the CSS community. Most of the removed CSS2 features will be made obsolete by CSS3.

Grammar and rules

Trident grammar and rule notes

1. @font-face — Only supports Embedded OpenType (.eot) font format, does not understand the format() identifier.
2. !important — !important doesn't override rules defined later in the same declaration block prior to IE7.

Tasman grammar and rule notes

1. @font-face — Versions 5.16 and 5.17 will download fonts specified but not use them. 5.23 no longer downloads the font.

Presto grammar and rule notes

1. @import — Whilst Gecko, WebCore and iCab download all media stylesheets immediately, Opera only downloads handheld, print, projection and screen media, as well as speech if "voice" feature is enabled and tv, on tv devices. Text browser emulation mode is only a user stylesheet, so it does not switch to tty media type. This is consistent with older text browsers, which do not respect any CSS.

Selectors

Trident selector notes

1. :active — :active is for anchor element only.
2. :hover — :hover is applied for all elements only in standards-compliant mode, not quirks mode [1]. Prior to 7.0, :hover is for anchor element only.
3. .one.two — only .two class selector was taken into consideration before 7.0.
4. * — Prior to 7.0 this was treated as a single or no element.

Tasman selector notes

1. :hover — For anchor element only prior to 0.9.
2. .one.two — only .two class selector is taken into consideration.

WebCore selector notes

1. :lang() — Only detected when explicitly present on element being tested, attribute not inherited.
2. :target — Style doesn't get applied when navigating using back and forward buttons.
3. :last-child & :last-of-type — will match all siblings, or all siblings of the same type, respectively.
4. :only-child & :only-of-type — identical behaviour to :first-child & :first-of-type.
5. ::pseudo-element — Mistakenly also triggers on ::pseudo-class prior to version 416.0.

Properties

Trident property notes

1. overflow — overflow:visible is incorrectly supported prior to IE7.
2. border-style — dotted is rendered as dashed prior to IE7.
3. display — Only none, block, inline, table-header-group, and table-footer-group are supported prior to 7.0. In 5.5+, inline-block is supported on elements that are naturally inline.
4. position — Prior to IE 7, fixed positioning was not supported, IE 7 supports it in standards-compliant mode only.
5. background-attachment — Prior to IE 7, fixed was allowed on the body element only.
6. background-position — Fixed positioning is not supported.
7. font-weight — Incorrect rendering when value is 600 [2].
8. text-decoration — Optional property blink is not supported.
9. white-space — nowrap is supported in IE 5.5 and later. pre is supported in IE 6 and later in standards-compliant mode. pre-line and pre-wrap are not supported.
10. list-style-type — decimal-leading-zero, lower-greek, lower-latin, upper-latin, upper-roman are not supported.

Gecko property notes

1. display — run-in [3] is not supported. inline-table [4] and inline-block [5] are supported in Gecko 1.9a2+.
2. quotes — Does not support nested quotes prior to 1.8 [6].
3. content — Only works with :before and :after. Only support image <uri>. <counter> does not work prior to 1.8 [7].
4. background-position — Gecko versions prior to 1.7 implement the CSS2 syntax, not the proposed CSS2.1 expanded syntax.
5. font-size-adjust — Supported in Windows only[8]. This problem will be fixed in the future Gecko 1.9.
6. font-weight — Only Regular and Bold weights get used, even if Light or Heavy/Black faces are installed.
7. white-space — pre-line is not supported. pre-wrap is only supported experimentally as -moz-pre-wrap;.
8. visibility — collapse is not supported prior to 1.8.
9. border-radius — border curves are circular, but the W3C specs [9] define them as elliptical. Dashed curves are not available. Short-cut definitions for border-radius read "tl tr br bl" instead of the W3C's "tr br bl tl". Interesting bugs: [10] [11] [12]
10. page-break-before; page-break-after — Only the always and auto values are supported.

WebCore property notes

1. box-shadow — The system font keywords are not supported that allow designers to tailor presentation to the user’s operating system environment.
2. font — The system font keywords are not supported that allow designers to tailor presentation to the user’s operating system environment.
3. font-weight — Only Regular and Bold weights get used, even if Light or Heavy/Black faces are installed.
4. page-break-before; page-break-after — Only the always and auto values are supported.
5. text-decoration — Optional property blink is not supported.
6. white-space — pre-line and pre-wrap from the proposed CSS2.1 draft are not supported.
7. text-shadow — Multiple shadows are not supported.
8. visibility — collapse is not supported prior to 522.

KHTML property notes

1. overflow — Values scroll and auto are unsupported.
2. page-break-before; page-break-after — Before 3.5 only the always and auto values were supported.
3. text-decoration — Optional property blink is not supported.
4. visibility — All supported except for collapse.

Presto property notes

1. list-style-type — The CSS2 values are not supported prior to 8.0.
2. counter-increment, counter-reset — Implemented the algorithm in REC CSS2.
3. background-position — Presto versions prior to 8.0 implement the CSS2 syntax, not the proposed CSS2.1 expanded syntax.
4. font-weight — Incorrect rendering when value is 600 [13].
5. white-space — pre-line is not supported.
6. visibility — All supported except for collapse.

iCab property notes

1. display — run-in is not supported.
2. text-align — justify is not supported.
3. font-stretch — Simulated using letter-spacing property.
4. font-weight — Incorrect (bold) rendering when value is 500.
5. visibility — collapse only partial.
6. caption-side — top and bottom only which would comply with the proposed CSS2.1 elimination of the values: left and right.
7. empty-cells — Compresses hidden rows but does not hide them completely.

Values and units

Trident value and unit notes

1. auto — In IE5 bug emulation mode (quirks mode) does not work for margins, except table elements.

WebCore value and unit notes

1. <percentage> — Only uses the integer component of <number>.

Presto value and unit notes

1. attr() — As all URI attribute values are resolved to full URI, the value could be wrong if attr() is used on an attribute that contains relative URI.
2. <number> — Quantization error for values greater than 20.47 [15] (not limited to em, try any non pixel units).

KHTML value and unit notes

1. rgba() — Because opacity is not supported, the opacity value of rgba() is ignored.

General notes

Gecko general notes

1. -moz- — All experimental selectors, properties and values are prefixed with "-moz-", e.g. ::-moz-selection instead of ::selection [16].

WebCore general notes

1. -webkit- — All experimental selectors, properties and values are prefixed with "-webkit-", e.g. -webkit-box-shadow instead of box-shadow.

KHTML general notes

1. -khtml- — All experimental selectors, properties and values are prefixed with "-khtml-", e.g. -khtml-opacity instead of opacity.

Presto general notes

1. -xv- — All new selectors, properties and values introduced by CSS3 Speech Module are prefixed with "-xv-" (but not found in CSS2 aural style sheets), e.g. -xv-voice-rate instead of voice-rate.

References

• W3C. CSS 1 test suite.
• W3C. CSS 2.1 test suite.
• mozilla.org Bugzilla. Bug 281960 - [devmo] Mozilla CSS support chart.
• Mozilla Developer Center. Mozilla CSS support chart.
• Opera Documentation. Web Specifications Supported in Opera - CSS.
• Internet & Web - Safari. CSS Support in Safari.
• Konqueror Homepage. CSS 2.1 & 3 Support in KHTML 3.4.
• Apple Developer Connection. Safari CSS Reference.

External links

CSS Compatibility Tables

• WebDevout — mostly covers Windows browsers. Extensive bug testing.
• QuirksMode — comprehensive but lacks latest versions.
• Westciv — abridged form of their retail guide.
• MacEdition — covers many Mac browsers, including rare and discontinued ones.
• Jesset — simple table without bug details, includes WebTV.
• Motohiko — covers Firefox only. [Japanese]

Other links

• CSS Filters — a fairly complete table of browser-specific hacks
• CSS specification/browser support page: General Syntax
• Assigning external CSS

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This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.