General :: Give Directory Permission To A Group And Not Specific User?

I'm trying to do something like thisi created a group called www and made this group the owner of the directory/var/www/htmlso i can read and write to it.of course I've add my self to this group, but it seems i can't read and write.the syntax i used was something like chown :www /var/www/html.didn't workonly when i used chown samurai:www /var/www/html i could finally could create new file.the reason i don't want to specify the user name is because I'm thinking of a scenario when i need to give permission to a large group of ppl and don't want to do it user by user.