Font tag <pre> text example
The lawnmower mowed the lawn. (29 characters)
Lilly Lilliput likes lillies. (29 characters)
The sly brown fox jumped quickly over the lazy dog 0123456789

Monospace text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.
The sly brown fox jumped quickly over the lazy dog 0123456789

Sans-serif text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.
The sly brown fox jumped quickly over the lazy dog 0123456789

Serif text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.
The sly brown fox jumped quickly over the lazy dog 0123456789

Cursive text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.
The sly brown fox jumped quickly over the lazy dog 0123456789

Fantasy text example
The lawnmower mowed the lawn.
Lilly Lilliput likes lillies.
The sly brown fox jumped quickly over the lazy dog 0123456789

Web safe fonts

The following fonts were designed specifically for readability on web pages and are considered web and browser safe due to their wide spread presence on both Macintosh and Windows platforms:

Georgia
Verdana

The web page http://shark.comfsm.fm/~dleeling/cis/dropdown_style.html allows you try out a wide variety of fonts, safe or not.

Arial: The sly brown fox jumped quickly over the lazy dog 0123456789
Tahoma: The sly brown fox jumped quickly over the lazy dog 0123456789
Avantgarde: The sly brown fox jumped quickly over the lazy dog 0123456789
Verdana: The sly brown fox jumped quickly over the lazy dog 0123456789
Times New Roman: The sly brown fox jumped quickly over the lazy dog 0123456789
Book antiqua: The sly brown fox jumped quickly over the lazy dog 0123456789
Bookman Old Style: The sly brown fox jumped quickly over the lazy dog 0123456789
Courier New: The sly brown fox jumped quickly over the lazy dog 0123456789

Windows Fonts: Macintosh Equivalent: Generic equivalent
Arial: Helvetica: sans-serif
Book Antiqua: Palatino: serif
Bookman Old Style: Bookman: serif
Times New Roman: Times: serif
Courier New: Courier: monospace

Credits:
http://www.utoronto.ca/ian/books/xhtml1/chap4/fig4-7.html
http://doc.web.cern.ch/DOC/usere/usfontse/usfontse.htm
http://www.htmlhelp.com/reference/css/style-html.html#span
http://www.wpdfd.com/wpdtypo.htm
http://doc.web.cern.ch/DOC/usere/usfontse/usfontse.htm

Stylesheet: http://www.comfsm.fm/~dleeling/turquoise.css