Guys it didnt help out..
But thanks a lot of effort by u all
i asked the my domain administrator whether custome error messages can be set or not ?
he said they can be set and he told me to give the links for error messages like 404,500 etc..
so it is clear that .htaccess will work in my site .. but how to do it by myself ??
Each and every time i may not able to contact him... please help guys !!!