Here's the info from their page:
Article from Tanger Outlets:
We want to give back to our fans! Help us get 50,000 new “likes” (96,000 total likes) by our Magic of Midnight After Thanksgiving Sale (November 26), and we will give all of our fans 50% off a $50 gift card! That’s a $50 gift card for only $25 just in time for the holiday season! Give it as a gift or use it for your holiday shopping. Start telling your friends now!
Here’s how it works…One the day that we hit 96,000 “likes”we will post a link visible exclusively to our fans. The link will only be up for 24 hours so don’t miss it. Click on the link to fill out your information. A voucher for your gift card voucher will be emailed to you. You will have 10 days to redeem your voucher from the day it was downloaded at your nearest Tanger Outlet store.
Hurry and go "Like" Tanger Outlets here