I have an HP photosmart it worked fine to print from my iPad until we had to change Internet. We now have a simple wireless router with no Internet. The iPad can see the printer but all efforts to print to it are refused as 'printer offline'.
I can print to this printer from my laptop and I can go to the IP address of the printer through safari and from there print a test page! I just can't print form any application to print something I need!
iPad 2, iOS 5.1.1