Firefox seems to send the "sign-in" POST request without a Content-Length header for the "sign-In" link on "elance.com". At least I assume that is the reason I couldn't login via Squid (411 ERROR saying length is required). IE works, which may be down to how they generate the requests on different browsers, as it sends a "Content-Length: 0" header in these requests. Is there a config that makes this work with Squid? (Currently using Debian Etch squid package 2.6.5-6). Have they done a known gotcha in their Ajax? Reproduce: Visit http://www.elance.com/ Click on "sign-In" No sign-in dialogue appears. When: Always with Firefox via Squid. Never with IE. Never with Firefox without Squid. Firefox 2.0.0.11 or Iceweasel 2.0.0.10 same, client Windows or Debian makes no difference. Error: 1200651675.192 1 212.24.80.83 TCP_DENIED/411 2658 POST http://www.elance.com/php/reg/main/signInAHR.php? - NONE/- text/html Tried "request_entities" option in the squid.conf no effect. Firebug happily shows a nice informative bit under "XHR" queries, including the full text of the Squid error - saying "knock it off with the malformed requests" (I paraphrase in local idiom to make it challenging for those that aren't native English speakers).