Non-Grounding outlets do not contain a ground contact and are often found in older homes. NEVER REPLACE A NON-GROUNDED OUTLET WITH A GROUNDED OUTLET.
Millions of homes still have 2-slot outlets in outlet boxes that are not properly grounded. As an alternative to expensive re-wiring, the NEC allows you to replace a 2-slot outlet with a GFCI even if there is no ground connection. GFCIs can safely accept 3-prong plugs.
