The URL listed is only one example. Most Hard Rock Cafes have the same offer, but especially if you're outside the US you'll want to look up your local cafe. The burgers are 71 cents (or a similar price using 71 in local currency). Similarly, *most* cafes run the special from 11-12, but some (at least overseas) are from 10-11 or only for half an hour in that general timeframe.
Some non-US locations have a different offer - for instance, Macau says, "To celebrate the brand's 47th birthday Hard Rock Cafe Macau will be offering guests a choice of signature entrees for MOP71 with the purchase of any item from the EATS Menu from June 8, 2018 to June 14, 2018!" while the Yokohama cafe has an "Our Birthday" event which says only, "Let's celebrate with hard rockers!"
For *most* Hard Rock Cafes, the offer is a classic burger for 71 cents (its original price), generally accompanied by live music and celebration of some sort. Also, for most cafes, the deal is good for only one hour only, June 14. Dine-in only. FIRST COME, FIRST SERVED