The Yandex spider is a frequent visitor to one of the sites I manage. On occasion it replaces the page name with two ampersands and a space. So if the page is: /mypage.aspx?param=value then it ...
Although I put a row for Yandex into my robots.txt file, sometimes Yandex indexes my website aggressively. So I hard coded a part and check for user agent, and serve cached file if user agent is like ...