HTML, XHTML & CSS

In addition to the font size names (xx-small,
x-small, small, medium, large,
x-large, or xx-large), you can also assign
font sizes by using the following CSS units
of measure: px (pixels), pt (points), or em (the
m-height for the font in use, whatever it may be).
Pixels depend on the size of an individual pixel
on your user’s display and will vary too much
from screen to screen to be truly useful. Points
are very small units of measure and may require
too much experimentation to get just right. That
The result appears in Figure 11-2.
Chapter 11: Getting Creative with Colors and Fonts
Sizing text fonts with CSS
Figure 11-2: First-level headings are twice as big as the base
font; font size for other text is relative.
Line height
The line height of a paragraph is the amount of space between each line
within the paragraph.
Line height is like line spacing in a word processor.
probably explains why em is the most widely
used unit in sizing fonts in CSS nowadays, and
why this approach is considered a best practice
for sizing fonts using stylesheets. Choosing
em units won’t free you from experimentation,
but it will make it quick and easy for you to size
type relative to your underlying font. For more
information on using these units, which take the
form font-size: 2em; (to double font size)
or font-size: 0.8em; (to reduce a font to
80 percent of the base), see Chapter 9.
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