pop-up options 

Allowpopupsites

If  u don't understand follow following link

To access the pop-up blocker settings: Click the menu button Menu and choose Options. Select the Content panel. pop-up options In the content panel: Block pop-up windows: Uncheck this to disable the pop-up blocker altogether. Exceptions: This is a list of sites that you want to allow to display pop-ups. Allowpopupsites The dialog has the following choices: Allow: Click this to add a website to the exceptions list. Remove Site: Click this to remove a website from the exceptions list. Remove All Sites: Click this to remove all of the websites in the exceptions list. If u don't understand follow following link https://support.mozilla.org/en-US/kb/pop-blocker-settings-exceptions-troubleshooting