Style Variables 
StyleVars (short for Style Variables) are PHP variables that contain a single value used to control the appearance of some aspect of a vBulletin style. Stylevars are used in conjunction with CSS and Templates to control the look and feel of your vBulletin site.

StyleVars are incorporated into CSS and Templates using the {stylevar} syntax. While Stylevars are primarily used within CSS in vBulletin, they can be used in XHTML templates as well.
User Contributed Notes: Style Variables