-> click Firefox button and click Options -> Content panel -> place/remove Checkmark from Block Pop-up windows -> click Exceptions... button -> type the addresses of the websites on which you want to Allow Pop-ups to appear e.g. msn.com , yahoo.com , google.com , etc. -> click Allow for each, One by One -> click Close

-> click Firefox button and click Options -> Advanced panel -> General tab -> Remove Checkmark from Warn me when websites try to redirect or reload the page

-> Click OK on Options window -> Restart Firefox

Check and tell if its working.

-> IF it still doesn't work, do this:

• Go to your concerned website
• Right-click empty space within the page and click View Page Info
• In the Page Info window, select the Permissions panel
• Under Load Images , Open Pop-up windows , Set Cookies, place/remove Checkmark on Use Default and change the setting to Allow
• Close the Page Info window

Check and tell if it works.

-> Also make sure that you are not using any Add-ons that can Block Pop-ups. If you are using such kind of an add-on, either Change its Settings to Allow on your concerned websites or Disable them.

• Troubleshooting extensions and themes - https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes

Here is a list of Blocking add-ons - https://addons.mozilla.org/en-US/firefox/search/?q=block

Open Options > Content and beside "Block popup windows", click the "Exceptions" button. Add the hostname of the site to the list. Alternately, if Firefox put a bar at the top of the page informing you that popups were blocked for the site, you can click "Allow", or make an exception from there.

@finitarry dude i already suggested it..

You can see the permissions for the domain in the current tab in "Tools > Page Info > Permissions"

Do you see an icon on the location bar to indicate that Firefox is blocking pop-ups on that website?