I needed to reinstall it. So reseted it to factory settings, connected with the usb cable (iMac) and reinstalled the driver.
I opened then its html configuration site. I intended to enable wifi support and input my network settings.
And here problems occured.
I marked "enable wireless" box and pressed "apply" button. The page went blank. I reopened printer's html config. The changes were not saved. I was not able to configure the printer. None of the changes I did were saved.
Fortunately I solved the problem after 2 hours. My question is why it is this way.
I recalled that when I bought the printer I connected it to the second (from the left) iMac's usb port as the first was already occupied. Its driver was then installed for the first time. Today I tried to configure the printer while it was attached to the first port.
So I plugged its usb cable into the second slot. Everything was ok then.
Why uninstall keeps such info in the system? Should I bother myself with the usb port used during the first install? I will start taking notes on it