I know it was probably a cookie, but that is some damn poor programming for a high traffic site (it was one of the majors, Northwest or the like).

I'm sure it was Northwest. I was the manager of the development team for that site, until March of this year. We must have had six bugs in our bugtracker that came and went regarding IE's mysterious handling of form data. It was completely unpredictable as to when a user could hit the back button and expect to see their form data intact, or when IE would decide to clear it out. And no, d33zY, it had nothing to do with refreshes.

We spent a disproportionate amount of time trying to track down and fix this particular bug, as it was seen as a big annoyance by the users. We tested many, many combinations of options in various combinations of IE releases and OS's. In the end, we could not find a rational explanation for IE's behavior, so we implemented a workaround that attempted to manually force the form elements to be set, based on cookie data. It did help in some cases, but in others, you'd get the behavior you reported (old search items being set in the form fields). It was a lose-lose situation.

I wonder how many erroneous bookings happen because of this.

About as many as you'd expect, and our development team had to help provide research data to support the customer service department in handling refund claims. Not an efficient structure, but we were at the mercy of the airline's will with this one.

It's now six months since I've left, and it sounds like the problem hasn't been solved yet. Perhaps they decided to punt, and simply accept the higher support costs.

--dan.