UIAlertView

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Title here" message:@"message here" delegate:self   cancelButtonTitle:@"OK" otherButtonTitles: nil];
[alert show];
[alert release];

- (void)alertView:(UIAlertView *)alertView

clickedButtonAtIndex:(NSInteger)buttonIndex {

if (buttonIndex==0) {

//any action when you press ok

}
}