Common Font Families found in Dreamweaver CS5, all at 24px:
Browsers will look for these fonts in the order listed.
Try to end with a generic font if you create your own font family

NOTE: The "generic" fonts will likely appear differently on different machines

Verdana, Geneva, sans-serif

Georgia, Times New Roman, Times, serif

Courier New, Courier, monospace

Arial, Helvetica, sans-serif

Tahoma, Geneva, sans-serif

Trebuchet MS, Arial, Helvetica, sans-serif

Arial Black, Gadget, sans-serif

Times New Roman, Times , serif

Palatino Linotype, Book Antiqua, Palatino, serif

Lucida Sans Unicode, Lucida Grande, sans-serif

MS Serif, New York, serif

Lucida Console, Monaco, monospace

Comic Sans MS, cursive