1. Apparatus for receiving, storing and discharging items, such as palletized cargo containers, for example, said apparatus comprising, in combination, a plurality of storage racks aligned in horizontal rows and vertical columns along at least one side of at least one aisle, the racks opening toward the associated aisle and each having a pair of laterally spaced horizontal rails extending perpendicularly to the associated aisle; a plurality of skids each comprising a grated frame constituted by a rectangular grid of rectilinear longitudinal and lateral components defining rectangular openings in the frame; a receiving station and a discharge station at one end of each line of racks, each station being aligned with a respective rows of racks and said stations being spaced vertically from each other, with each station having a pair of laterally spaced horizontal rails extending perpendicularly to the associated aisle; an item receiving conveyor extending to said receiving station; an item discharge conveyor extending from said discharge station; respective fork lift means movable longitudinally of each aisle to transfer items, supported on skids, between said racks and said stations; respective skidders mounted for vertical displacement at each station for movement into and out of horizontal alignment with the respective rails at the associated station, each skidder having a main frame to receive and support a grid, and a secondary frame movable vertically relative to said main frame and carrying rollers movable through openings of said main frame and through the openings in a grid supported on said main frame to engage, lift and support an item resting on the grid supported on said frame; and a skid feeder laterally adjacent said station and extending vertically therebetween, said skid feeder including means opeRable to receive unloaded skids from the skidder at said discharge station, move the unloaded skids vertically to said receiving station, and feed the unloaded skids onto the skidder at said receiving station; the skidder at said receiving station, prior to delivery of an item thereto on said item receiving container, being raised into horizontal alignment with the rails at the receiving station to receive and support an unloaded skid fed from said skid feeder, and its secondary frame being moved upwardly to project its rollers through the openings of the skid to receive the item from said receiving conveyor, after which the secondary frame is lowered for the item to rest on the grid and the skidder at the receiving station is lowered in its entirety to rest the skid on the rails at the receiving station for removal of the loaded skid from the receiving station by the associated fork lift means; the skidder at said discharge station, upon delivery of a skid-supported item to said discharge station by the associated fork lift means to rest on the rails of said discharge station being raised into alignment with the rails to support the skid and the item, and its secondary frame being moved upwardly to project its rollers upwardly through the openings in the grid to engage and lift the item on the grid for transfer to said discharge conveyor, the secondary frame then being lowered and the unloaded grid being moved from the skidder at the discharge station to said skid feeder.