I found the offer on this page:
http://www.united.com/page/article/0,6722,51357,00.html

United Airlines

drugstore.com
Earn award miles for your health and beauty products. Spend up to $100 and earn 5 award miles for every $1 spent. Spend more than $1000 and earn 10 award miles for every $1 spent.

Limited time offer: Earn 1,000 bonus award miles when you make your first purchase by Dec. 31, 2010.