HTML and CSS Reference
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A ppendix A serves as a full reference to all CSS 2.1 properties, including basic browser sup-
port information for the four most commonly used desktop browsers: Firefox, Safari, Opera,
and Internet Explorer.
CSS Units, Keywords, and Other Property Values
CSS includes a fixed set of units and keywords as values for several of its properties. The first
section of this appendix covers these property values. Later in the appendix, when we cover
individual properties you'll find references to these predefined values.
Factors and Integers
Numeric values in CSS can be either factors (decimal numbers) or integers (whole numbers).
In most cases, negative versions of both are allowed.
CSS colors can be specified as a red, green, and blue (RGB) value, a hexadecimal value, or one
of 17 predefined color name keywords. Few web designers use RGB values. Hexadecimal is the
most common method used, followed by color keywords.
A hexadecimal value is the hash symbol, or pound sign ( # ), followed by pairs of hexadecimal
digits specifying red, green, and blue components of the intended color. Hexadecimal digits
are numbers or letters in the range 0-9 or a-f. Three-digits shortcuts in the form #rgb can be
substituted for #rrggbb .
Examples: #50017c , #d0cecf , #dfdfdf , #f80 , #9c0