How do I format a memory card for a digital camera?

Try formatting the memory card, open the camera's Menu and select Format memory card.
You may want to copy the photos before formatting the SD memory card.

If you format the memory using the PC then the memory card may not work in your camera. Format the memory card using the camera, go to the camera's menu and scroll through the settings until you come to Format the memory card, then select it and Format the memory card.

If you cannot format the memory card using the format function of the camera, please connect the camera to your computer and use the computer to access your memory card and format fromt the computer.

Alternatively you can also use a memory card reader and connect the memory card to your reader and connect it inturn to your computer and format it from the computer

Use this option to format the internal memory or memory card. Formatting the Internal Memory To format the internal memory, remove the memory card from the camera. The [Format memory] option appears in the setup menu.
Formatting the Memory Card
When the memory card is inserted in the camera, the [Format card] option appears in the setup menu.
or for more detail get the user manual from here
http://www.nikonusa.com/pdf/manuals/coolpix/L12_en.pdf
do rate the solution if helped

Format error display shows memory card is unstable and need to be format through format option in Camera menu.
Format memory card, if that does not fix the issue, try another memory card in camera and check this memory card in another camera just to make sure either camera got problem or memory card is bad.

Try formatting your camera memory card If you own camera memory cards that have been used in other digital cameras, the card may not be properly formatted for use in your camera, or that data on the card may become corrupted. When these issues arise, your camera indicates that the camera memory card needs to be formatted.
When you format a camera memory card, all of the information on the card is erased. This includes any borders supplied on the card.

1. Set the Mode dial to Camera Setup.
2. Slide the POWER switch to the right to turn on the camera. The main Camera Setup screen appears.
   
3. Press a button until the icon is highlighted.
4. Press the DO-IT button. The Format Memory Card screen appears.
   
5. Press a button until CONTINUE FORMAT is highlighted.
6. Press the DO-IT button to format the camera memory card and return to the main Camera Setup screen.

Take out memory card from camera, turn it On and check does it show format error?
If yes, press Home, Memory option and format internal memory.
If camera does not show format error then put back memory card in and press Home, Memory card option and format it.
This will delete all files/ data and will refresh memory card, take some pictures and check.
If after formatting, still format error exist, put new memory card.

instead of quick format, use the full format.  Then put back in your camera and format again with the camera.

The Polaroid PDC 700 digital camera accommodates an optional, Type 1 ATA compatible CompactFlash memory card up to 48MB. When an unformatted memory card is installed in the camera, it is automatically formatted when the camera is powered on. WARNING: Once you format the flash memory or format a memory card, all images are erased and cannot be retrieved - they are gone forever! Before you format (erase) the flash memory or format a memory card, transfer the images to your computer.

If you used the SD/MMC memory card in another brand of camera or device, you may need to format the card in your new EasyShare digital camera. (You may have noticed a "Memory Card Needs Formatting" message when you inserted the card.) CAUTION: Formatting deletes all pictures and videos, including those that are protected. Removing a card during formatting may damage the card. To format the SD/MMC memory card or the internal memory of the camera: Transfer images to the computer before formatting the memory card. Press the camera Menu button. Highlight SETUP MENU, and then press the OK button. Highlight FORMAT, and then press the OK button. Highlight an option - MEMORY CARD (deletes everything on the card), CANCEL (exits without formatting), or INTERNAL MEMORY (deletes everything in internal memory). Press the OK button. Highlight Continue, and then press the OK button. Wait until formatting is finished before removing the card. When formatting is complete, the SETUP MENU is displayed. Press the Menu button to exit the menu.