Milan, this is another great contribution from you to the spread of web standards!
As Nikhil Kothari and Chris Ward have said I think the key is thinking your site in a semantical way by applying standard XHTML, and using CSS to create the visual layout. The standard XHTML, the semantical structure of your site that repeats itself on each page like the global navigation of the site, can be centralized by the use of master pages.
I've been investigating the subject in the last few days and I think the
MasterPages Templating Framework at MetaBuilders provides a really simple solution for the problem and one of the most compatibles with the upcoming Master Pages on ASP.NET 2.0.
Are you using something similar on this site for templating?
You'd probably read it already, I'm currently reading
designing with web standards and can certainly recommend it to have fun learning about the whole semantical concept of the web. =)