filtering web sites for users

[tselvan]

hi,       we r using cisco 1720 router connected to isp thru a serial interface.   router is  inturn connected to an ethernet interface to serve the users. we  want to filter certain web sites like mp3.com, yahoo.com as we r using the leased line for office use. we have tried out the following using access-list:    access-list  100 deny tcp 63.241.16.56 0.0.0.0 192.168.1.0 0.0.0.255     63.241.16.56 - for mp3.com    192.168.1.0-  for user network.   when we tried out this  users were unable to browse.   pl suggest for an alternate access control list.   beno