My example works for me with Preview and Adobe Reader, in both cases 
Safari opens the PDF on page 58.

Wolfgang
> Hans van der Meer <mailto:havdmeer@ziggo.nl>
> 18. April 2018 um 21:12
> I have the following question about referencing.
>
> With \goto{typeset_the_text}[url(file://a_file_location_to_goto 
> <file:///a_file_location_to_goto>.pdf)] I can open a pdf from inside 
> the document that has been typeset. It would, however, be nice if I 
> could further specify on which page of the pdf to open. Is this 
> possible? Or is this a wish not to be fulfilled?
>
> dr. Hans van der Meer
>
>
> ___________________________________________________________________________________
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> to the Wiki!
>
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> ___________________________________________________________________________________
> Wolfgang Schuster <mailto:schuster.wolfgang@gmail.com>
> 18. April 2018 um 21:58
> For documents on the web you can add #page=<NUMBER> to the url.
>
> \setupinteraction[state=start]
>
> \starttext
> \goto{Beginners 
> manual}[url(http://pragma-ade.com/general/manuals/mp-cb-en.pdf\letterhash 
> page=58)]
> \stoptext
>
> Wolfgang
>
> Hans van der Meer <mailto:havdmeer@ziggo.nl>
> 18. April 2018 um 23:04
> Thanks. But this seems not to work on my Macintosh. Not in Preview, 
> not in Adobe Reader.
> Typesetting resulted in valid-url.pdf#page=55 but the document opens 
> at the last page remebered by the application. Are there other 
> Macintosh users who can confirm this is not working on those machines 
> or should I do something else?
>
> dr. Hans van der Meer
>
>
>
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry 
> to the Wiki!
>
> maillist : ntg-context@ntg.nl / 
> http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage : http://www.pragma-ade.nl / http://context.aanhet.net
> archive : https://bitbucket.org/phg/context-mirror/commits/
> wiki : http://contextgarden.net
> ___________________________________________________________________________________