pkg_add vs portmaster

[Mage]

         Hello,

why is that

"pkg_add -r x11/kde4" could not install kde4 (404 not found) but 
"portmaster -P x11/kde4" did, however
"portmaster -P xorg" didn't install xorg (it just reinstalled some 
modules) then "pkg_add -r xorg" installed it.

I am a bit confused with these.

I was reading this:
http://freebsd.kde.org/
and this:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/x-install.html

First I installed kde4 then xorg. My ports are up to date.

         Mage