I had a similar problem with my 96. Funny thing was, it was loose for a long time, and when some guy was test driving it, it just fell on him... Yeah, that makes the car look good...
Basically, there are two screws inside there, and for one reason or another they jsut wiggle themselves loose, if you pull off the bulb part you can get to where you replace the bulbs, no there wont be any screw hole here, you have to remove this as well, underneath that is a spot for a couple of screws, give them a good tighten down and reassemble, should be all set.
