Xcode: iPhone app codesign error
The fix is pretty simple. In the Build Results window (which you probably got to by clicking the error icon in the lower right corner of your project window), change the pulldown menu from ‘Device - iPhone xxx’ to ‘Simulator - iPhone xxx’.
(source: kickasslabs.com)
You need to be part of the $99 developer program to test on the actual phone. Apple should have info about how to sign your code once you're accepted into the program.
I got this error when I accidentally modified the code signing identity build setting at the target rather than the project level. Make sure that you have the correct information entered at the project level (get info on the project, rather than the target.) If you changed the target build settings, try deleting the values from there. The target will then inherit the project's setting.
I would also do a "clean all", then exit xcode, delete everything from the build folder and try to do another build. (This is an Xcode voodoo trick that seems to solve many code signing issues.)