Below, you'll find information about pop-ups for some popular browsers but, because browsers are updated frequently, it may be best to view your browser's help pages for the most up-to-date information on how to enable pop-ups.
Microsoft's FAQ shows you how to turn Internet Explorer's pop-up blocker on and off.
Similar to Firefox, in Chrome, you can add specific sites to an allowed list so pop-ups for that site always appear. For more information on how to manage pop-up settings in Chrome, have a look at Google's support documentation.
In Firefox, you can add specific websites to an allowed or exceptions list. Once you add a site to this list, pop-ups from that site are always visible. Mozilla's support pages show you how to manage pop-up blocker settings in Firefox.