Introduction to CSS (Cascading Style Sheets) with JavaScript - JavaScript by Example - page 535

Table 14.1 Style Sheet Properties (continued)

Property Value/Example Tags Affected

Margins and Borders (Continued)

margin-right 20em,45% All

margin-top 1cm, 20% All

padding 2em, 4em, 6em (right, bottom, left) All

padding-bottom 2em, 20% All

padding-left .25in, 20% All

padding-right .5cm, 35% All

padding-top 20px, 10% All

width 12em, 30%, auto (initial width value) Block-level and

replaced element a

a. A replaced element has set or calculated dimensions, such as img, select, textarea .

14.4.1 Units of Measurement

You can express the size of a given property in different units of measurement; for exam-
ple, a font size can be expressed in pixels or ems or points (the default is pixels). Colors
can also be expressed in combinations of red, green, and blue, either by the name of the
color, or its hexadecimal value.
Measurement is used in three categories: absolute units, relative units, and proportional
units. For example, a point size measurement (e.g., 14pt ) would be the actual size (absolute)
of a particular font; a value (e.g., 5em) could be relative to the size of the current font; and a
color (e.g., 50%80%100% ) could represent red, green, and blue as a percentage value of the
original color. Relative sizes larger and smaller (relative to the parent font) can be used when
defining a font. These sizes are determined by browsers or other user agents. 2 Tables 14.2
and 14.3 introduce the types of measurements that are often used in style sheets.

Table 14.2 Font Size Units

Absolute Font Size Unit

inches (in)

centimeters (cm)

Continues

2. User agents include Web browsers, search engine crawlers (spiders), cell phones, screen readers, and
Braille browsers used by people with disabilities.