As it works on any client when they bypass the proxy, I guess the problem not ony come from the client. But I'll get a log from firefox tomorrow @ work if needed. One thing I forgot to mention, my Squid is configured in High Anonymous and in transparent mode. This is one of the popup which cause the problem(can be viewed as web page): http://consent-pref.truste.com/?type=ibm&site=ibm.com&action=notice&country=fr&locale=fr&behavior=expressed&from=http://consent.truste.com/&url=http://www.ibm.com/us/en/ I think something is not well accepted by my Squid but I don' t know what. and this is it source code: <!doctype html> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1"> <noscript> <div style="width: 22em; position: absolute; left: 50%; margin-left: -11em; color: red; background-color: white; border: 1px solid red; padding: 4px; font-family: sans-serif"> Your web browser must have JavaScript enabled in order for this application to display correctly. </div> </noscript> </body> </html> Thx HErC.