He discovered an accidental error in his composition 他在作文里发现了一个意外的错误。
2.
An unexpected error occurred 发生意外的错误!
3.
The following sections discuss how you can mitigate potential security risks that are exposed by unexpected error messages and events 以下各节讨论如何减轻由于意外的错误信息和事件而暴露的潜在安全风险。