In our lan we use Firefox (various versions, from 8 to 23, also 17 ESR releases) on windows computers (xp and 7 32 bit) . We require a http proxy authentication (squid) with username and password. We usually configure only Internet Options in windows control panel checking the flag on "use automatic configuration script" with an url like "http://proxy/proxy.pac". In this script we give a list of intranet sites (web applications) that don't require a proxy authentication on internet because are internal sites on our lan. So on firefox we use the option "Use system proxy settings". The issue is: during a session on those intranet sites the firefox dialog window for proxy authentication often appears annoying the operator who has to close it every time. We have tried to mitigate the problem disabling firefox automatic updates, add-ons updates, search engines updates, do not track requests, attack sites and web forgeries lists updates, telemetry, health and crash reports. It seems not to be enough to solve the problem. Are there other settings to set in "about:config" page? workarounds? add-ons? Thanks for your help in advance. PS: sorry for my english, I'm still learning.