You're over-thinking the implementation.
Make sure that your BODY tag has a call to body_class():
<body <?php body_class(); ?>>
And that the DIV (or other container) that holds your posts has a call to post_class():
<div <?php post_class(); ?>>
These will add CSS classes for you, including author-specific classes. See the linked Codex references for further information.
This topic has been closed to new replies.