I created a framework for common tasks such as XML parsing, buttons and so on.
Can I upload my application in App Store if it uses this framework? I saw somewhere that App Store did not support private frameworks. Is this a private framework, even though I created it using Apple's libraries, such as UIkit, Foundation, etc.?
Look at the similar question - you cannot use dynamic libraries in your application and should build and use static library instead.
Relevant abstract from iPhone OS overview:
The iPhone SDK supports the creation of native foreground applications that appear on the device’s Home screen only. It does not support the creation of other types of code, such as drivers, background applications, frameworks, or dynamic libraries. If you want to integrate code from a framework or dynamic library into your application, you should link that code statically into your application’s executable file when building your project.
You cannot use your own Framework on the iPhone, instead you have to statically compile your library with your application. A minor annoyance but not a show stopper.