[Yashas]

You have to #define FILTERSCRIPT (actually remove that comment line in the script)
Or else your filterscript will be considered as a gamemode.

And another possibility:

Wait,Wait,Wait Did you add the filterscript in server.cfg ??
You have type "filterscript [filename]" and dont add the extension of the file.
Suppose the file is abc.amx, in server.cfg it must be "filterscripts abc"