when installing to a specific directory such as
./configure --prefix=/usr
do you have to use the prefix for make and make install also???

sorry for so many questions

When you run the './configure --prefix=/usr' command, it generates a Makefile which contains the instructions for make and make_install. You should not have to specify the prefix for make and make_install. If you have any doubts, after you run ./configure, and before you run make, edit the toplevel Makefile, and verify that prefix=/usr. The toplevel Makefile is located in the highest level directory for the app you want to install: example: if you install to a directory /usr/local/<appname>, the toplevel Makefile is in <appname>. Subdirectories of <appname> will also have their own Makefiles. But, as I said, the ./configure command with the prefix option should correctly write the Makefiles.

ok, but now i have another directory question, what does this mean

checking for KDE... configure: error:
in the prefix, you've chosen, are no KDE headers installed. This will fail.
So, check this please and use another prefix!

i chose /usr, where would these headers be?