JavaScript (not Java) opens that window.

Do you have JavaScript enabled?

• Options > Content > (x) Enable JavaScript

Other-

You need to update some other applications on your system that install plugins in Firefox. All of the following that are installed on your system have security issues that have been corrected in more current versions:
Shockwave Flash 11.2 r202
Next Generation Java Plug-in 1.6.0_29 for Mozilla browsers
Adobe PDF Plug-In For Firefox and Netscape "9.5.0"

• Check your plugins - https://www.mozilla.org/en-US/plugincheck/
• Flash - https://support.mozilla.org/en-US/kb/install-flash-plugin-view-videos-animations-games
  • Flash download for Firefox - http://download.macromedia.com/get/flashplayer/current/licensing/win/install_flash_player_11_plugin.exe
• Java - https://support.mozilla.org/en-US/kb/use-java-plugin-to-view-interactive-content
• Adobe Reader (PDF) - https://support.mozilla.org/en-US/kb/use-adobe-reader-plugin-view-or-download-pdf-files

Thanks for the hints. Here is my response:

• JaveScript is enabled (always was)
• I updated all plugins (see attached image)
• The only plugins, I did not update are:
  • Microsoft Office 2010 (unknown plugin)
  • ActiveTouch General Plugin Container (unknown plugin)
  • QuickTime Plug-in 7.7 (Outdated Version but not vulnerable - I'm not a big QuickTime user, hence didn't want to update)

Result of above things: No change. Popups still don't open.

Note: I also use NoScript but it is set to "Allow all except blacklist" so JavaScript is not blocked because the pages I visit are all clear.

Can you suggest another path of action for my issue?

Best, Alex

I also use NoScript, but temporarily allow sites as I feel that offers the best security. I use Request Policy add-on for finer-grained control of NoScript. I only had to temporarily allow thomann.de in NoScript for the pop-up window to appear. And I have "Block pop-up windows" checked with no exceptions listed.

• Have you tried clicking on the NoScript icon to see if thomann.de is listed as being blocked? If so allow it and/or add it to the NoScript whitelist to see if the page works.
• https://support.mozilla.org/en-US/kb/settings-fonts-languages-pop-ups-javascript
• https://support.mozilla.org/en-US/kb/pop-blocker-settings-exceptions-troubleshooting

My only other suggestion would be to try Firefox Safe Mode to see if an extension is interfering (maybe a firewall/anti-virus toolbar). If it works in Firefox Safe Mode you will need to restart Firefox to enable your extensions, then disable one or two at a time, restart Firefox, and repeat until you find the offender.

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

If all else fails, use Reset mentioned in the Safe Mode article. You will need to reinstall your extensions, a few at a time, then test, after the reset.

• Read carefully what Reset does and does not do - https://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems

Re-reading your response, I noticed "I also use NoScript but it is set to "Allow all except blacklist"". Where is that option in NoScript? How does it interface with a blacklist as NoScript does not have a built-in blacklist?

I simply deinstalled noScript. So noscript was the reason. I did not check which of noscript's numerous settings was the actual reason for the problem. I still like NoScript.

Must have been caused by some quirk in your NoScript settings as the site works fine for me with NoScript installed, after temporarily allowing the site in NoScript.

You can inquire on the NoScript forum - http://forums.informaction.com/viewforum.php?f=3 (registration is required)