It's possible I'm not in the right place, but i'm using www.linkcat.info, which is Wisconsin's South Central Library System's patron-facing ILS. I know they use Koha for their back end, and I believe it also generates the patron-facing portions (a supposition supported by matching js code and folder-naming on linkcat).
When a patron clicks on Cancel to cancel a hold, linkcat responds with a generic Window.confirm() (via koha-tmpl/opac-tmpl/prog/en/modules/opac-user.tmpl -> koha-tmpl/opac-tmpl/prog/en/js/script.js:confirmDelete()). In this particular case that dialog is pretty confusing because it uses Cancel/OK for its options. See attached screenshot.
