Getting pop-up error "Netscape.cfg/AutoConfig failed" when trying to drive firefox via selenium Grid using Watir-Webdriver


Get Error:

Netscape.cfg/AutoConfig failed. Please contact your system administrator.
 Error:  defaultPref failed: [Exception... "Component returned failure code:  0x8000ffff (NS_ERROR_UNEXPECTED) [nsIPrefBranch.setBoolPref]"  nsresult:  "0x8000ffff (NS_ERROR_UNEXPECTED)"  location: "JS frame :: prefcalls.js  ::  defaultPref :: line 58"  data: no]

Netscape.cfg/AutoConfig failed. Error:  defaultPref failed: [Exception... "Component returned failure code:  0x8000ffff (NS_ERROR_UNEXPECTED)

I have the following setup:

Selenium Grid on CentOs 6.4

Slave Node = CentOs 6.4

Trying to run Firefox remotely via Watir-WebDriver

require "rubygems"
require "test/unit"
#require "selenium"
require "watir-webdriver"

caps = Selenium::WebDriver::Remote::Capabilities.firefox
#caps.version = "24"
caps[:name] = "Firefox 24  , port 5555"

default_profile = Selenium::WebDriver::Firefox::Profile.from_name "default" 
default_profile.native_events = true 
driver = Selenium::WebDriver.for(:firefox, :profile => default_profile)

    @browser =
    :url => "http://vm-auto.his.vm:4444/wd/hub",
    :desired_capabilities => caps)

    @browser.goto ""
    @browser.text_field(:name => "q").set "3M"
    @browser.div(:id => "resultStats").wait_until_present ("GoogleSearch_FF24.png")

Firefox version is Mozilla Firefox 24.7.0

there is a reference to this error in

the resolution being suggested as:

In my case commenting out this pref in mozilla.cfg stops generating this message.
But I do not know origin of this pref.

//stops the request to send performance data from displaying
//pref("toolkit.telemetry.prompted", true);

But, i could not find mozilla.cfg on the filesystem where firefox is installed

asked on Stack Overflow Aug 15, 2014 by kamal

2 Answers


I had the same issue with Firefox 24 ESR. Mozilla.cfg was in the same directory as the Firefox executable. In my case this was under "%localappdata%\Microsoft\AppV\Client\Integration[Unique-Code]\Root". I commented out 'pref("toolkit.telemetry.prompted", true);' and the error message didn't appear anymore.

answered on Stack Overflow Dec 3, 2015 by Virtuoso

That error definitely seems to be related to a problem in the mozilla config file BUT in my case the file was not mozilla.cfg but mozilla-lock.cfg (located at C:\Program Files (x86)\Mozilla Firefox\).

The filename is dictated by the lockset.js file at C:\Program Files (x86)\Mozilla Firefox\defaults\pref\. The line is pref("general.config.filename", "mozilla-lock.cfg")

My issue with the config file was the following lines:

lockpref("security.tls.version.min", "1");
lockpref("security.tls.version.max", "3");

The values should be without quotes:

lockpref("security.tls.version.min", 1);
lockpref("security.tls.version.max", 3);

As addendum, it's entirely possible you don't have a config file at all and the problem exists with a manual configuration in the about:config. Open up the about:config page, and sort by 'status' to look for 'locked', 'user set' or any other non 'default' items.

answered on Stack Overflow Jul 29, 2016 by duct_tape_coder • edited Jul 29, 2016 by duct_tape_coder

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