XHTML 1.1 which is mainly a modularization of XHTML 1.0, is composed of 20 element modules (7 of which are submodules), including the additional Ruby Annotation Module, and two attribute modules (Server-side Image Map Module and Intrinsic Events Module).
Values indicate the level of support in the most recent version of the layout engine, or (if a version number is given) in the specified version. Version numbers without any other value indicate the version at which the layout engine first fully supported the feature.
Indicates that the layout engine fully supports this property/element when valid values are used.
Indicates that the property/element is completely ignored.
Indicates that the property/element is understood, but that not all values are supported. Supported values are implemented correctly.
Indicates that the property/element is understood, but that it is not implemented correctly in all cases.
Indicates that the property/element is understood, but supported under an alternate name. May be incomplete or buggy.
Indicates that the property/element is no longer supported.
^All style tags after the first 31 style tags are not applied.
All style rules after the first 4,095 rules are not applied.
On pages that uses the @import rule to continuously import external style sheets that import other style sheets, style sheets that are more than three levels deep are ignored.