After setting up ncsa_auth in squid (FreeBSD 6.3), Java applets wouldn’t run. I found this link that solved it.

<blockquote>You can solve this by creating an acl like this:
acl java_jvm browser Java/1.4 Java/1.5 Java/1.6
http_access allow java_jvm <p>Remember to keep it in front of any http_access lines regarding authentication, otherwise it won’t work.</p></blockquote><p> </p>