My sony cyber shot DSC F717 digital camera has a problem. when turned on, no images on the screen. as well in the view finder.

This problem could be a number of things.
Does it allow you to have any access to the menus? If you can get to the menus, try setting the menus to default settings. Test the camera after setting the menus to default.

Can the camera play back images or videos and show on the screen? If they can be seen, then possible some setting is not right.
If you cannot see images when in recording mode try the play back mode and see if you can see any images in the lcd.
If you cannot see any images in either play back or record mode, and no menus, then the camera needs to be repaired.

If you can see images when you play back, and none when in record mode, then the ccd is suspected to be defective. If that is so, call Sony, give them your camera model and serial to see if they can repair the camera. The status will have to be determined by Sony repair.