for user based Authentication I configured use ncsa_auth just following steps
#touch /etc/squid/squid_passwd
#chmod o+r /etc/squid/squid_passwd
#htpasswd /etc/squid/squid_passwd vishal
New password:
Re-type new password:
Adding password for user vishal

#
# Add this to the auth_param section of squid.conf
#
auth_param basic program /usr/lib/squid/ncsa_auth /etc/squid/squid_passwd

#
# Add this to the bottom of the ACL section of squid.conf
#
acl ncsa_users proxy_auth REQUIRED

#
# Add this at the top of the http_access section of squid.conf
#
http_access allow ncsa_users
but when I access web from othr system I get dialog box asking to enter username & password. but it's not accepting n giving error cache access denied. pls. help.

change that to

even if that doesnt work change the user/passwd file from squid_pass to squid.pass

try it shd work