Sophistication, freedom, rebellion or just the simple joy of taking to the open road with the wind in your hair. The convertible car used to represent all of these. But over the past two decades sales have collapsed, and its future seems deeply uncertain. So what's gone wrong? In the 1950s and 60s, owning a convertible showed you had style. They were what the celebrities of the era were seen in. When Hollywood deities Grace Kelly and Cary Grant were shown cruising along the French Riviera in a