User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1) Gecko/20061003 Firefox/2.0 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1) Gecko/20061003 Firefox/2.0 When i set an automatic proxy configuration URL in Network Settings, i have got some big latence when i load a bad url and sometimes even with valid URL. Here is my proxy.pac : function FindProxyForURL(url, host) { if ((isPlainHostName(host) || isInNet(host, "10.0.0.0", "255.0.0.0") || isInNet(host, "163.5.0.0", "255.255.0.0") || isInNet(host, "172.16.0.0", "255.255.0.0") || isInNet(host, "127.0.0.1", "255.0.0.0")) && !isInNet(host, "163.5.254.25", "255.255.255.248") && !isInNet(host, "163.5.254.16", "255.255.255.248") && !isInNet(host, "163.5.69.0", "255.255.255.0") && !isInNet(host, "163.5.254.0", "255.255.255.0") ) return "DIRECT"; else return "PROXY proxy-adm.epita.fr:3128"; } This happens for all the students of my school who use the same settings than mine. Reproducible: Always Steps to Reproduce: 1. Configure an automatic proxy configuration URL 2. Type a wrong URL and press ENTER 3. Wait ..... till it times out Actual Results: Lattence

I have the same bug with version 1.5 and 1.0

I can confirm this. Even more. During that lag, normally I can't do anything with the browser, and many times I must close it. The problem is in the command isInNet. I thnik it happens when I ask for an URL with a long ping time, or when IP cannot be retrieved. If IP cannot be retrieved (unknown host if I ping to it), navigator uses a lot of time in sentences like: if (isInNet(host, "10.34.32.228", "255.255.255.255") { ..... } If I delete al sentences that chek host ip, then there is no lag

This is a duplicate of bug 235853. https://bugzilla.mozilla.org/show_bug.cgi?id=235853 Go add your votes to 235853, it is driving me crazy.

NEW.

This is a duplicate of bug 208287.