Looks to me like the include path for your 18F4250.h file is not defined or defined incorrectly. You'll want to set them for CCS, in MPLAB go to the "Project" menu and select "Set Language Tool Locations..." and point CCS include path to where you have your Devices folder for CCS. I've attached an example picture of how mine is set.
Once you do that, you'll overcome your missing file problem, but then run into other compile issues which I haven't looked at yet.
Your program looks like it's written for the Microchip C18 Toolsuite, your include file should be defined like:
#include <p18f4520.h>
And you should also have that at the beginning of your timer.h file
If you want to use CCS, you're going to need to rewrite your code to support that compiler.
ok then ,how to write a code ,which supports ccs compiler ?
can u give me any example code for pic18f4520 ic
and I included the search path as u told,
but what about open directory ,intermediate directory,library search path& linker script search path.what path i should give here.