Click on Tools, Pop-up Blocker
if the pop-up blocker is set to Turn on Pop-up Blocker.
Click on it to disable the pop-up blocker.
Click on Tools, Options
In the Options window click on Content and uncheck the Block pop-up windows box.
Visit the site where you want pop-ups to always appear.
Click the Pop-ups Blocked alert at the bottom right-hand corner of the browser tab.
Select Always show pop-ups from (site).
If you want to change this setting for the site at a later point, follow these steps:
Visit the site again.
Click the Manage pop-ups alert at the bottom right-hand corner of the browser tab.
Deselect Always show pop-ups from (site).
Click on Safari menu in the upper-left hand corner of the screen.
Click on Block Pop-up Windows, there you can then toggle the pop-up blocker off by un-checking.