HTML and CSS Reference
In-Depth Information
Defining Values for Four-Sided Properties
Properties such as
margin
,
padding
, and
border-width
are used to
define values for all four sides of a block (whereas
margin-right
defines the right margin alone). These properties, and those like
them, can take from one to four space-separated values that are
applied to the sides in the following manner:
■
If one value is listed (for example,
10px
), that value is applied to all
four sides.
■
If two values are listed (for example,
10px
5%
), the first value is
applied to the top and bottom, while the second is applied to the
right and left sides.
■
If three values are listed (for example,
10px
5%
20px
), the first value
is applied to the top, the second to both the right and left sides,
and the last to the bottom.
■
If four values are listed (for example,
10px
5%
20px
auto
), the values
are applied clockwise starting from the top (top, right, bottom, left).
At-Rules
At-rules are statements that begin with the character for at (
@
), followed
by a rule type or identifier, and end with a semicolon. Unlike rule sets,
at-rules do not contain declarations directly but offer additional context
or commands for the processing of style sheet information. Here's an
example:
/* include file additional.css */
@import “additional.css”
/* target specific media with contained rules */
