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which one is correct?

This cannot be made if the cookie function on your webreader is shut off.

This cannot be made if the cookie function in your webreader is shut off.
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I would say in.
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webreader: use (web) browser
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Comments  
Surprise: I'd say of or I wouldn't use a preposition at all.

My sentence would be:

This won't work (can't be done) if cookies are disabled in your browser.

or

This won't work (can't be done) if you have your browser set to disable (reject) cookies. (alternatively: set to not accept cookies.)

I like the latter sentence much better.

P.S. I'm quite sure that many handbooks could say your webreader's function.
Surprise: I was thinking of oftoo Emotion: big smileEmotion: stick out tongue, but then I considered thatin might also be appropriate.
PastsimpleP.S. I'm quite sure that many handbooks could say your webreader's function.
I don't like 's there; to me, your webreader cookie function sounds much better.
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 Marius Hancu's reply was promoted to an answer.