Don't know where you got those instructions. Try these instructions (Tools > Options > Content):

• http://support.mozilla.com/en-US/kb/Pop-up+blocker

Other issues needing your attention

The information submitted with your question indicates that you have out of date plugins with known security and stability issues that should be updated. To see the plugins submitted with your question, click "More system details..." to the right of your original question post. You can also see your plugins from the Firefox menu, Tools > Add-ons > Plugins.

• Next Generation Java Plug-in 1.6.0_23 for Mozilla browsers
  • Security update version 1.6.0_24 released 2011-02-10

1. Check your plugin versions: http://www.mozilla.com/en-US/plugincheck/
   • Note: plugin check page does not have information on all plugin versions
2. Update the Java plugin to the latest version.
   • Download site: http://www.oracle.com/technetwork/java/javase/downloads/index.html (Java Platform: Download JRE)
     • Be sure to un-check the Yahoo Toolbar option during the install if you do not want it installed.
   • Also see "Manual Update" in this article to update from the Java Control Panel in Windows Control Panel: http://support.mozilla.com/en-US/kb/Using+the+Java+plugin+with+Firefox#Updates
   • Removing old versions (if needed): http://www.java.com/en/download/faq/remove_olderversions.xml
   • Remove multiple Java Console extensions (if needed): http://kb.mozillazine.org
   • Java Test: http://www.java.com/en/download/help/testvm.xml

Those instructions are very out of date, they refer to Firefox 1. Updating those instructions for the current version of Firefox:

1. Open Mozilla Firefox
2. Click Tools
3. Click Options
4. Click Content on the top of the Options Window
5. By default this feature should be enabled if you wish to disable the feature, uncheck "Block Popup Windows." If you have allowed popups on a site you wish to now block you can also click "Exceptions" in this window and remove any sites you wish to block any popup on.

This article has more information - https://support.mozilla.com/kb/Pop-up+blocker

Thanks, TonyE. It was staring me in the face. I am so darn literal minded. You've helped in my fight against popups. If I could only resolve the pop UNDER problem. Best regards.

Oran