Abstract
This specification describes the margin and padding properties, which create spacing in and around a CSS box.
CSS is a language for describing the rendering of structured documents (such as HTML and XML) on screen, on paper, etc.
Status of this document
The following features are at-risk, and may be dropped during the CR period:
- applicability of margin, padding and their longhands to ruby base containers and ruby annotation containers
“At-risk” is a W3C Process term-of-art, and does not necessarily imply that the feature is in danger of being dropped or delayed. It means that the WG believes the feature may have difficulty being interoperably implemented in a timely manner, and marking it as such allows the WG to drop the feature if necessary when transitioning to the Proposed Rec stage, without having to publish a new Candidate Rec without the feature first.
Conformance
Document conventions
Conformance requirements are expressed with a combination of
descriptive assertions and RFC 2119 terminology. The key words “MUST”,
“MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”,
“RECOMMENDED”, “MAY”, and “OPTIONAL” in the normative parts of this
document are to be interpreted as described in RFC 2119.
However, for readability, these words do not appear in all uppercase
letters in this specification.
All of the text of this specification is normative except sections
explicitly marked as non-normative, examples, and notes. [RFC2119]
Examples in this specification are introduced with the words “for example”
or are set apart from the normative text with class="example",
like this:
This is an example of an informative example.
Informative notes begin with the word “Note” and are set apart from the
normative text with class="note", like this:
Note, this is an informative note.
Advisements are normative sections styled to evoke special attention and are
set apart from other normative text with <strong class="advisement">, like
this: UAs MUST provide an accessible alternative.
Conformance classes
Conformance to this specification
is defined for three conformance classes:
- style sheet
- A CSS
style sheet. - renderer
- A UA that interprets the semantics of a style sheet and renders
documents that use them. - authoring tool
- A UA that writes a style sheet.
A style sheet is conformant to this specification
if all of its statements that use syntax defined in this module are valid
according to the generic CSS grammar and the individual grammars of each
feature defined in this module.
A renderer is conformant to this specification
if, in addition to interpreting the style sheet as defined by the
appropriate specifications, it supports all the features defined
by this specification by parsing them correctly
and rendering the document accordingly. However, the inability of a
UA to correctly render a document due to limitations of the device
does not make the UA non-conformant. (For example, a UA is not
required to render color on a monochrome monitor.)
An authoring tool is conformant to this specification
if it writes style sheets that are syntactically correct according to the
generic CSS grammar and the individual grammars of each feature in
this module, and meet all other conformance requirements of style sheets
as described in this module.
Partial implementations
So that authors can exploit the forward-compatible parsing rules to
assign fallback values, CSS renderers must treat as invalid (and ignore
as appropriate) any at-rules, properties, property values, keywords,
and other syntactic constructs for which they have no usable level of
support. In particular, user agents must not selectively
ignore unsupported component values and honor supported values in a single
multi-value property declaration: if any value is considered invalid
(as unsupported values must be), CSS requires that the entire declaration
be ignored.
Implementations of Unstable and Proprietary Features
To avoid clashes with future stable CSS features,
the CSSWG recommends following best practices for the implementation of unstable features and proprietary extensions to CSS.
Non-experimental implementations
Once a specification reaches the Candidate Recommendation stage,
non-experimental implementations are possible, and implementors should
release an unprefixed implementation of any CR-level feature they
can demonstrate to be correctly implemented according to spec.
To establish and maintain the interoperability of CSS across
implementations, the CSS Working Group requests that non-experimental
CSS renderers submit an implementation report (and, if necessary, the
testcases used for that implementation report) to the W3C before
releasing an unprefixed implementation of any CSS features. Testcases
submitted to W3C are subject to review and correction by the CSS
Working Group.
Further information on submitting testcases and implementation reports
can be found from on the CSS Working Group’s website at https://www.w3.org/Style/CSS/Test/.
Questions should be directed to the [email protected] mailing list.
CR exit criteria
For this specification to be advanced to Proposed Recommendation,
there must be at least two independent, interoperable implementations
of each feature. Each feature may be implemented by a different set of
products, there is no requirement that all features be implemented by
a single product. For the purposes of this criterion, we define the
following terms:
- independent
- each implementation must be developed by a
different party and cannot share, reuse, or derive from code
used by another qualifying implementation. Sections of code that
have no bearing on the implementation of this specification are
exempt from this requirement. - interoperable
- passing the respective test case(s) in the
official CSS test suite, or, if the implementation is not a Web
browser, an equivalent test. Every relevant test in the test
suite should have an equivalent test created if such a user
agent (UA) is to be used to claim interoperability. In addition
if such a UA is to be used to claim interoperability, then there
must one or more additional UAs which can also pass those
equivalent tests in the same way for the purpose of
interoperability. The equivalent tests must be made publicly
available for the purposes of peer review. - implementation
-
a user agent which:
- implements the specification.
- is available to the general public. The implementation may
be a shipping product or other publicly available version
(i.e., beta version, preview release, or “nightly build”).
Non-shipping product releases must have implemented the
feature(s) for a period of at least one month in order to
demonstrate stability. - is not experimental (i.e., a version specifically designed
to pass the test suite and is not intended for normal usage
going forward).
The specification will remain Candidate Recommendation for at least
six months.
Index
Terms defined by this specification
Terms defined by reference
-
[css-backgrounds-3] defines the following terms:
-
background
-
background-clip
-
background-origin
-
border
-
-
[css-break-4] defines the following terms:
-
box fragment
-
box-decoration-break
-
fragmentation break
-
-
[css-cascade-5] defines the following terms:
-
longhand
-
longhand property
-
shorthand property
-
-
[css-display-3] defines the following terms:
-
block layout
-
box
-
box tree
-
containing block
-
internal table element
-
replaced element
-
-
[css-pseudo-4] defines the following terms:
-
::first-letter
-
::first-line
-
-
[css-ruby-1] defines the following terms:
-
ruby annotation container
-
ruby base container
-
-
[css-sizing-3] defines the following terms:
-
sizing property
-
-
[css-transforms-1] defines the following terms:
-
transform-box
-
-
[css-values-4] defines the following terms:
-
<length-percentage>
-
css-wide keywords
-
{a,b}
-
|
-
-
[css-writing-modes-4] defines the following terms:
-
flow-relative
-
logical width
-
physical
-
writing mode
-
-
[DOM] defines the following terms:
-
document tree
-
-
[SVG2] defines the following terms:
-
canvas
-
object bounding box
-
stroke bounding box
-
svg viewports
-
user coordinate system
-
viewbox
-
References
Normative References
Informative References
Property Index
Name
Value
Initial
Applies to
Inh.
%ages
Animation type
Canonical order
Computed value
margin
<‘margin-top’>{1,4}
0
all elements except internal table elements, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
see individual properties
margin-bottom
<length-percentage> | auto
0
all elements except internal table elements, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
the keyword auto or a computed <length-percentage> value
margin-left
<length-percentage> | auto
0
all elements except internal table elements, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
the keyword auto or a computed <length-percentage> value
margin-right
<length-percentage> | auto
0
all elements except internal table elements, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
the keyword auto or a computed <length-percentage> value
margin-top
<length-percentage> | auto
0
all elements except internal table elements, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
the keyword auto or a computed <length-percentage> value
padding
<‘padding-top’>{1,4}
0
all elements except: internal table elements other than table cells, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
see individual properties
padding-bottom
<length-percentage [0,∞]>
0
all elements except: internal table elements other than table cells, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
a computed <length-percentage> value
padding-left
<length-percentage [0,∞]>
0
all elements except: internal table elements other than table cells, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
a computed <length-percentage> value
padding-right
<length-percentage [0,∞]>
0
all elements except: internal table elements other than table cells, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
a computed <length-percentage> value
padding-top
<length-percentage [0,∞]>
0
all elements except: internal table elements other than table cells, ruby base containers, and ruby annotation containers
no
refer to logical width of containing block
by computed value type
per grammar
a computed <length-percentage> value
