★★★
  by accident
偶然地,意外地
 
 
I won first prize by accident!
我意外地贏了頭獎。
I saw an old friend on the street by accident.
我在街上偶遇一位老朋友。

by chance
luck

建議使用最佳瀏覽解析度﹕IE 5.0 以上版本 800 x 600