W3C CSS2 Cascading Style Sheets, level 2 - instructional media + ...

mm: millimeters
pt: points -- the points used by CSS2 are equal to 1/72th of an inch.
pc: picas -- 1 pica is equal to 12 points.
Example(s):
H1 { margin: 0.5in } /* inches */
H2 { line-height: 3cm } /* centimeters */
H3 { word-spacing: 4mm } /* millimeters */
H4 { font-size: 12pt } /* points */
H4 { font-size: 1pc } /* picas */
In cases where the specified length cannot be supported, user agents must
approximate it in the actual value.
4.3.3 Percentages
The format of a percentage value (denoted by in this specification)
is an optional sign character (’+’ or ’-’, with ’+’ being the default) immediately
followed by a immediately followed by ’%’.
Percentage values are always relative to another value, for example a length.
Each property that allows percentages also defines the value to which the
percentage refers. The value may be that of another property for the same
element, a property for an ancestor element, or a value of the formatting context
(e.g., the width of a containing block [p. 96] ). When a percentage value is set for
a property of the root [p. 30] element and the percentage is defined as referring
to the inherited value of some property, the resultant value is the percentage
times the initial value [p. 69] of that property.
Example(s):
Since child elements (generally) inherit the computed values [p. 70] of their
parent, in the following example, the children of the P element will inherit a value
of 12pt for ’line-height’, not the percentage value (120%):
P { font-size: 10pt }
P { line-height: 120% } /* 120% of ’font-size’ */
4.3.4 URL + URN = URI
URLs (Uniform Resource Locators, see [RFC1738] and [RFC1808]) provide the
address of a resource on the Web. An expected new way of identifying resources
is called URN (Uniform Resource Name). Together they are called URIs (Uniform
Resource Identifiers, see [URI]). This specification uses the term URI.
URI values in this specification are denoted by . The functional notation
used to designate URIs in property values is "url()", as in:
Example(s):
BODY { background: url("http://www.bg.com/pinkish.gif") }
The format of a URI value is ’url(’ followed by optional whitespace [p. 37]
followed by an optional single quote (’) or double quote (") character followed by
the URI itself, followed by an optional single quote (’) or double quote (") character
followed by optional whitespace followed by ’)’. The two quote characters
must be the same.
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