> It would actually be better that all browser-dependant things were
> managed on server side, producing documents dynamically and in case then

It would be better if pages simply provided information and left the
user agent to deal with rendering.  Some examples of where servers
side customisation fail are:

- minority browsers - the browser capabilities known to the server are
  often out of date or too conservative, and authors often reject 
  out right rather than try to support them;

- downloading for offline processing - you might download with wget
 (or even Internet Explorer) then use a completely different browser
 to view;

- non-browser tools - the advantage of structural markup is that you
  can add value by working with the content rather than the rendering -
  the classic case is search engines - and their owners don't take 
  kindly to pages that are content negotiated just for them.