Does the person who taught others how to display pornographic files bear their sins, and what is the expiation for that?

You did not intend to teach your friend how to open pornographic files, but rather how to open files in general, and what happened was by divine decree. Allah Almighty says: "And there is no blame upon you for that in which you have erred, but [blame is due for] what your hearts intended." And the servant is commanded to repent, and Allah accepts the repentance of those who repent and forgives sins. You must hasten to repent and do good deeds, and we hope that you will not bear sin for what your friend and those who followed him committed, as long as you did not intend evil and advised him not to teach anyone.