I discoverd that in iOS 10.3.2 (german language set, timezone Berlin / MESZ) in my iPad not every information concerning history and tracking could be deleted:
Following Einstellungen (Setting), Safari, Erweitert (more or extended), Website-Daten (website data) there is a list of pages visited (I assume with cookies set). When I'm trying "delete all" none of the entries will disappear. I tried additionally deleting one by one. By entering this part of setting again (even without using safari in the meanwhile) there are some of the entries there again, some of them with 0 bytes. Resetting / rebooting iPad or cleaning history completely before deleting or combination of different steps cookies still are there.
Are the domains which are listed in some sense untrustworthy? Or do they use some "irregular" code / approach? The most persistant ones are
Additional some google-domains (domains containing string google) and spiegel.de could be very often seen. Or some new sort of supercookies (but they are flash aren't they - and iOS does not support flash)? Or bug in iOS?