Sometimes you will be outbid as soon as you enter your bid, even though the bid you entered was higher than the current bid shown on the item listing. When this happens, you will usually be notified immediately in your current bidding page and given a chance to make another bid.
This happens because another buyer had a higher maximum bid (MaxBid) than yours. Your bid prompted our automatic bidding system to raise the other buyer's bid above yours. The other bidder may have placed their bid hours or days before.
NOTE: If you and another bidder had the same maximum bid, the earlier bid would win.
More about maxbid's here: maxbid
More about tied bid here: Same Bid?