Popups not blocked

From MozillaZine Knowledge Base
Revision as of 12:07, 28 August 2015 by Alice Wyman (talk | contribs) (→‎Hover ads)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigationJump to search

Mozilla browsers will block most pop-up and pop-under advertisements by default. (These are regarded as the same thing in this article.) If you are getting unwanted popups, try the following suggestions.

First steps

Your first step should be to make sure that the internal popup blocker is enabled in your browser and that you haven't "whitelisted" the sites that are giving you popups:

  • Firefox: "Tools -> Options -> Content (Web Features in Firefox 1.0.x)". Make sure the box "Block Popup Windows" is checkmarked. Click the "Allowed Sites" button to review the sites where popups are allowed and remove unwanted sites from the list.
  • SeaMonkey: "Edit -> Preferences -> Privacy and Security -> Popup Windows". Make sure "Block unrequested popup windows" is checked. Review the "Allowed Sites" list as above.


Some popups opened through JavaScript are beyond the realm of the internal blocker [1] (at least for now). Such popups can be prevented by disabling JavaScript completely within the browser, but this will prevent many sites from functioning correctly. Instead, you may use an extension to block these popups.

Conventional popups

Conventional popups can be blocked using a popup blocker extension. Alternatively, you can use the NoScript extension to allow only certain sites to use JavaScript, or you can use the Adblock Plus extension with filters applied.

Hover ads

Hover ads are a special form of popup. You can use either NoScript or Adblock Plus to prevent them.

Popups generated by other software

Sometimes other software that has nothing directly to do with Mozilla browsers can cause windows to pop up. Sources of such non-browser popups include the following:

Spyware on Windows

Pop-ups may be caused by spyware, a collective term for a type of malicious software that gathers information about the user. Spyware mainly affects Windows users and can be installed without your knowledge. Some recommended free spyware detectors and cleaners include:

If these don't find it or can't clear it, post in one of these forums for specialized malware removal help:

Messenger Service on Windows

In their initial state, Windows NT, 2000 and XP SP1 allow anyone on the Internet to initiate pop-up messages on your screen via the built-in Messenger Service (not to be confused with the Windows Messenger or MSN Messenger instant messaging clients). The title of these popups is always "Messenger Service". It is recommended that you disable this service. (This service is disabled by default in Windows XP SP2.)

Other software disables the popup blocker

The McAfee Privacy Service software is reported to disable your Mozilla browser's popup blocker, even if that software is uninstalled and you recheck the popup blocker option in your Mozilla browser. This happens because McAfee's software has set the related preference "dom.disable_open_during_load" to "false" via the user.js file and the popup blocker is again disabled when you restart the browser [2]. You can fix this as follows:

If the software is no longer installed, open the profile folder and delete (or rename) the user.js file. Alternately, if you don't want to delete the file because it contains other customized settings, open the user.js file in a text editor and delete the offending user_pref("dom.disable_open_during_load", false); preference line. When you restart your Mozilla application, you will then be able to recheck the popup blocker option and the setting will be retained. Note 1: this may still not enable your popup blocker if McAfee has also scribbled its text in other files. If Firefox still comes up with the popup blocker disabled, then do a file contents search for the text string dom.disable_open_during_load in all files in the Firefox directory (and subdirectories). Note 2: In some cases, even Note 1 will not fix things. If still stuck, do a similar string search in all files of the C:/Documents and Settings directory (and subdirectories). If you find such a file with this text string, delete it.

If the software is still installed and you try deleting the user.js file or the offending entry, it will be added back when the McAfee Privacy Service next starts (e.g., on reboot or when restarting the service). This applies even if you've told McAfee not to block popups. The solution (reported here) is to allow the 'controlling' program, McAfee, to grant popup-blocking privileges, as follows:

  • Go into McAfee Security Center, select 'internet and network', 'configure', 'web browsing protection', 'advanced'
  • Select the box to block popup ads, then restart the computer.

Popups from plugins

Firefox (1.5 and above) and SeaMonkey block popups from plugins (such as Flash) by default. See the article privacy.popups.disable_from_plugins for additional information.

Error alert popups

By default, Firefox (1.5 and above) and SeaMonkey use error pages instead of "error alert popups", such as "The operation timed out..." and "The document contains no data". See the article browser.xul.error_pages.enabled for additional information.

More effective pop-up blocking

A more effective way of blocking unwanted pop-ups is to install the "Adblock Plus" extension along with subscribing through its options to a filter such as "EasyList" to effectively block pop-ups, and other annoyances. You can add your own filters as well and they are maintained separately from your filter subscriptions. Targeting specific third party styles sheets and JavaScript inclusions can not only stop pop-ups but reduce other annoyances and malware as well.

To extend the capabilities of "Adblock Plus" you might also install Adblock Plus: Element Hiding Helper" extension to block specific elements on a page. Helps if you are familiar with HTML and CSS with this one because it is very easy to scrub out the entire web page with something that is too inclusive.

(Windows users) You should also install a hosts file on your system which will help with all browsers and applications, see Blocking Unwanted Parasites with a Hosts File. This method is primarily directed at the really bad sites, the most frequently encountered annoying ads, and sites known to try to modify your system.

Related preferences

See also

Blocking bad sites and annoyances

External links