In order to avoid confusion in typing your class/id names from memory, it is best to follow some sort of naming convention. With a proper naming convention, there will be no question on how you have structured your names.
What does CSS allow?
CSS is a case sensitive language. Using camel case class or id names (.className) leaves your naming convention open to future typo errors. Since XHTML elements are all in lower-case, and we are already using these elements in our stylesheets, it would be logical to follow that course with CSS names.
CSS allows for hyphens in the names of classes and ids. Since it is one of the only languages that allows for hyphens in names, we ought we not to exploit this? This also allows for greater readability to anyone who must go reading our stylesheet, since we are now using lower-case names.
Find more suggestions on naming conventions at PHPied’s article CSS Coding Conventions. I linked to this article before, but it’s just so applicable and sensible that I must link again.
