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Explanation of Terms

This reference uses CSS-specific terminology in its field headings. This article describes these terms and explains their meanings and possible values.

Contents:

Syntax
Types Allowed
Constants
Subproperties
Availability
Support Level

Syntax

The Syntax field describes the syntax of a CSS property. If a property can have multiple forms, each form appears in its own line.

Types Allowed

The Types Allowed field contains information about what numeric types are allowed in a given property. This field is missing from properties that do not have a single numeric type, such as properties that take multiple values or use non-numeric constants exclusively.

The Types Allowed field does not present the complete story, however, as a property may also take additional types specific to its subproperties.

Constants

The Constants field contains a list of non-numeric values that you can assign to a specific property. For example, the border-width property can take the value caption.

The Constants field does not present the complete story, however, as a property may also take additional values specific to its subproperties.

Subproperties

The Subproperties field describes properties that make up a larger property.

There are three basic types of properties: simple properties, convenience properties, and composite properties.

• Simple properties take a single value of a single type (or a single named constant, such as thin).

• Convenience properties (border-width, for example) combine multiple properties of the same type into a single value, and may optionally allow multiple values for each of the included properties.

• Composite properties (border, for example) take multiple values of different types.

Convenience properties such as border-width have related subproperties with finer granularity. For example, instead of setting the border-width property, you could set the border-bottom-width, border-top-width, border-left-width, and border-right-width properties to the same value and achieve the same result.

Because these convenience properties can be broken down into subproperties of the same basic type, any value that is legal for all of the subproperties is also legal for the convenience property as a whole if the property has a single-value form, and for the individual parts if the property has a multi-value form. For example, the border-width property can accept the value thin even though it is only listed in related subproperties such as border-bottom-width. Similarly, you could use a multi-value form, such as border-width: thin thin thin thin.

Composite properties also have related subproperties. For example, the second parameter in the border property is equivalent to the border-width property. Thus, any value that is appropriate for the border-width property is also appropriate for the width portion of the border composite property.

Similarly, the types allowed for a subproperty are also allowed for convenience properties and the appropriate portions of composite properties that contain them.

Availability

The Availability field tells the version of Safari in which the property first appeared.

Support Level

The Support Level field tells which revision of the W3C standard a given property is defined in, where applicable, and tells the overall status of the property for properties that are not part of a W3C standard. The possible values are:

• CSS 2.1—properties in CSS 2.1 and earlier revisions. These properties are fully supported across most major browsers, including Web Kit and Safari.

• Stable CSS 3—properties new in CSS version 3 but believed to be stable. Apple is committed to supporting these properties going forward and does not expect their syntax or names to change. Unlike more experimental CSS 3 properties, these properties are not prefixed by -webkit-, and many are supported by other browsers such as Internet Explorer or Firefox.

• Apple extension—properties defined by Apple. These properties are fully supported by Web Kit and Safari. A few of these extensions, where noted, are specific to Dashboard widgets or Safari on iPhone. Some of these extensions may have been submitted to the W3C CSS working group for standardization, but are not currently part of the latest draft standard.

• Experimental CSS 3—properties new in CSS 3. The syntax for these properties may change, but because they are prefixed by -webkit-, Apple believes that the current syntax can be supported going forward. You will still need to update these properties to the final CSS 3 syntax (as needed) and remove the -webkit- prefix if you need to use them on other browsers.

• Under development—new CSS 3 or Apple extension properties that are likely to change in syntax. Although it is OK to use these, support for these properties may change in incompatible ways in the future.

Properties may be upgraded to more stable categories as time passes, particularly as tags are added to relevant standards.

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