Hi,
You do not display a simple product listing.
You should use a filter or something like that. When you arrived to the product listing, a HTML post is done.
Because this "post" is done, when you want to come back to the listing, your internet browser knows that in order to have the same result, it has to resubmit the same post data to the server.
By default the browser do not re-submit a past post without the authorization of the user. That's why you have this warning message which is not an error message at all.
If you use a simple link which point to the product listing, you won't have such problem.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.