Thanks for your reply.
I used Drop on Top option, did not change any code manually. Currently, urls are looking like this:
http://localhost/catalog/index.php/hardware-c-1?osCsid=lgc6p2c5ma18b1ls6ep4qg8m04
I want to display it like:
http://localhost/catalog/index.php/hardware.html or for sub categories:
http://localhost/catalog/index.php/hardware/cd-rom-drives.html