Requote

[Pharaoh]

The price changed between the time you send the order and the time the broker tried to execute it. You can either cancel the order or accept a worse price. This can happen with any broker during fast moving market conditions. Bad brokers will do this to steal a few pips even during very calm markets.

I've composed a haiku on the subject:

Order requoted
Bucketshop or fast market?
Trade profit now gone