I cannot find some apps, what's going on? It always says "The requested item could not be found".

AppBrain lists applications that are available in the US that are available for Android version 1.6 and up for devices with a normal screen size. Developers can restrict availability of apps by country, Android version and screen size. This means that if you're not in the USA, have a device with a small screen size (for instance the HTC Wildfire or Tattoo), or when you're not on the latest version of Android, you may often get the "not found" message from the Android market.