can someone tell me exactly how i can build a thrd level domain like this
http://subDomain.domain.com ?

Then

is cache,db,cookie,context ... of a page in the third level domain available
in the second level domain? i mean if i can consider the pages in the thrd
level domain like a page within the  main domain site

If this is for IIS, you simply create new domains within your IIS zone (or
create new zones) and configure the appropriate host headers.

If this is for AD, and you want an actual domain (replication and
"administrative" boundary) then you run DCPROMO.  If you want a dis-joint
namespace take a look at this:
-- http://www.msresource.net/content/view/40/46/


If you want something else please elaborate what...

I need exactly something like the link in your signature:

http://forums.msresource.net ,

but i don't know how to make this in windows server 2003

Hmmm...Create a new domain in the DNS zone for the parent.  Then configure
the necessary host header in IIS.

As far as I'm aware, that's it.  The new domain in the existing zone will
create a (Same as parent) record that will respond to the domain name.  I'd
have to look at Internet Services Manager to talk more about IIS.  I've not
done much with IIS other than the basics (although, in this case I believe
the basics cover it ;-)

error with ntdsutil
Modify bulk users in AD
Group Policy item applies the first time I login then no more
How to do maintenance repair in AD
Hello Everyone ? On searching Active Directory
cleaning all user created files on logoff
Logon Problem on One Client
Identifying obsolete computer/user accounts in AD
Network Question
Export cert from CA