Nominative and Accusative Case of the Pronoun оно
Pronouns are not nouns. Neuter nouns do coincide in the Nominative and the Accusative cases in the Russian language:
Вот окно. Here is the window.
Я вижу окно. I am seeing a window.
But they do not coincide when neuter pronouns are used.
Оно красивое. It is beautiful.
Я вижу его. I am seeing it.
As far as I know, it happens in all Slavic languages.