What does it mean when my miner shows rejected or stale shares?

A rejected or stale share is work your miner submitted that the pool could not credit, usually because someone else found the same block microseconds earlier or the share arrived after the round closed. A small rate, around one to two percent, is completely normal and not worth worrying about. If rejects climb higher, the usual causes are an unstable or slow network connection, a pool server that is far away, or an aggressive overclock that makes the hardware produce occasional invalid results. Try a closer pool server first, then check your connection, then dial back any overclock. You are not losing your valid shares; only the late or duplicate ones are dropped.