Re: "active" CSS

> In my opinion, do not try to cross-contaminate the uses of each area, 
> leave "Behavior" to scripting, leave Markup to HTML/xhtml and leave Style 
> to CSS ;-)

Generally, that seems prudent, although it is not always feasible.  In this 
case, scripting may be the best way to go, but in some cases it is not.  For 
example, link-targeting, which seems more structural than presentational, 
has had to be added to CSS 3 for Strict DTD pages because it was expunged 
from the strict HTML and XHTML specifications and scripting is not a 
reliable way to target links because users may simply disable scripting 
completely--something they are unlikely to do to CSS.  Of course, CSS 3 will 
not be an especially reliable way to target links for some time either, but 
it should happen eventually.