RE: Will behaviors be added to CSS?

>> And how about CSS linking extensions implemented in Opera? These
>> extensions seem to be very useful and provide very flexible linking
>> mechanism for XML documents.

> What are they then? Any links to what you mean?

See Opera CSS linking extensions at http://www.opera.com/docs/specs/ 
the idea is to attach linking behaviour to arbirtary XML element via CSS,
for example you use XML markup like
<go to="http://www.opera.com/docs/specs/">Link</go>
and want to tell browser that "go" element should be handled as hyperlink 
with URL specified by "to" attribute, in Opera you can do it by setting 

go[to]
{-o-link:attr(to);
-o-link-source:current;}

This way is very practical and flexible and could be used with any XML 
markup.