How to make Squid 3.3.8 a transparent proxy?

[Tobias Krais]

i together,

I just upgraded Ubuntu 12.04 to 14.04 and with it I upgraded squid to 
3.3.8. I am using a Dansguardian / Squid content filter on my localhost. 
Dansguardian ist correctly working after the upgrade, but not Squid.

Here is my goal: configure Squid as a transparent proxy listening on 
port 3128.

Here is me current squid.conf:
-----%<-----
acl SSL_ports port 443
acl Safe_ports port 80        # http
acl Safe_ports port 21        # ftp
acl Safe_ports port 443        # https
acl Safe_ports port 70        # gopher
acl Safe_ports port 210        # wais
acl Safe_ports port 1025-65535    # unregistered ports
acl Safe_ports port 280        # http-mgmt
acl Safe_ports port 488        # gss-http
acl Safe_ports port 591        # filemaker
acl Safe_ports port 777        # multiling http
acl CONNECT method CONNECT
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost manager
http_access deny manager
http_access allow localhost
http_access deny all
http_port 3128 transparent
coredump_dir /var/spool/squid3
refresh_pattern ^ftp:        1440    20%    10080
refresh_pattern ^gopher:    1440    0%    1440
refresh_pattern -i (/cgi-bin/|\?) 0    0%    0
refresh_pattern (Release|Packages(.gz)*)$      0       20%     2880
refresh_pattern .        0    20%    4320
-----%<-----

With the config above, squid starts correctly. But when I want to access 
a website, squid says: "Access denied".

I tried hours all solutions I found in Google, but none worked. Can you 
please help me?

Greetings,

Tobias