HP deskjet D2300 series printer is showing offline .Power is already given to the printer.

Check that the printer is turn on, if on turn it off and on again, secondly check by double clicking the printer icon on your pc start bar i,t will open a pop/dialogue box, click on file and see if the offline is tick if so disable the tick.

Hello,
I am asuming a few things, one the printer is plugged into the PC, and the other its turned on (plugged into the wall, green light on power button).

Go into control panel. Start button> Control panel (or start button, Settings, Control panel). Select in the top left switch to classic view (gives you more options). Go into the item that says Printers, or printers and faxes. Right click on your printer in there, and select "Use Printer Online". Hope it works for you.