146 C HApter 9 u sing p Hone g Ap b uild The specification includes the means to define a single set of application icons (a home screen and optionally, for BlackBerry, a hover image) and a loading screen (splash) image. Unfortunately, application icon resolution (and sometimes graph- ics file format) varies across mobile device platforms and even across mobile devices. To fix this particular problem (and others), the PhoneGap Build develop- ers have implemented some PhoneGap and PhoneGap Build­specific settings to the options available in the config.xml file. As of this writing, the PhoneGap Build development team is still making enhance- ments to the features, options, and configuration settings for the service. Because of this, it's best to refer to their up-to-date documentation for specifics on the supported config.xml file options. Anything I wrote here about those settings could be nullified at any time by the PhoneGap Build development team. Detailed information about the PhoneGap Build­supported settings can be found at http://build.phonegap.com/docs/config-xml. One of the things I learned when working with the service is that when building applications for iOS, PhoneGap Build requires that the config.xml file's widget element contains an id attribute that contains a unique in reverse domain format, as shown in the following example: