I try not to ever use it
I find the site so difficult to use that I never use it. I either use our corporate travel system, when I'm booking a flight at the same time, or I call Hertz directly. I find it faster and easier, and I'm somebody who like to book ALL travel online. The Hertz site just doesn't cut it, from a usability perspective.
Coupons from Hertz are another can of worms, too. I've used them twice, on reservations booked by telephone. Both times, I've had trouble. And I had to stand on line at a counter and hand the coupons over, which meant the normal #1 Club Gold super-fast pickup just didn't happen.