If you have developed your Android application with the 1.5 SDK (or earlier), then your application won’t show up on the Android Market for users with devices with a lower screen resolution, like for instance the HTC Tattoo, HTC Wildfire, or Sony Ericsson X10 mini.
This is of course very unfortunate for both the user and you! The user won’t be able to use your wonderful application, and you’re missing out on an entire user base. This is a user base that is, growing and growing, since the smaller size devices are very popular among people that usually wouldn’t consider the larger smartphones.
But don’t despair, with just a couple of minor fixes you’ll be able support the smaller devices as well, since the Android OS, and the 1.6 version of the SDK handles most things for you.