The "ask me" option doesn't work either. Local storage is active always.

Regarding Dragonfly: Marvellous feature!
I'm able to check what's going on in local storage, e.g. googleads.g.doubleclick.
Now I'd want to autoclear the local storage upon closing of opera...

Sorry for not responding earlier.
I had set the option "use application cache" to no. But despite that, it is being filled with data. I'll try the "ask me" option. Meanwhile I had the suspicion that other web sites are also using the application cache as alternative cookie storage. When your'e caring about privacy, and you don't realize it, that's quite tricky.

Question: how can I inspect the contents of such data. Prior to deleting it, I'd like to check whether session data is stored.

It was the local storage. Thanks for the hint. I can see that several sites stored information in "local storage". Hm, a sort of cookies that I cannot automatically have deleted upon exit. Such a storage seems not to exist in Firefox, since the "test" yields no issues as complained here.

I'm used to have cookies deleted upon exit automatically. Just now, I was wondering upon a visit of klm.com where a flight inquiry re-appeared that I entered some weeks ago. This happens with Opera 12.16 (Linux). I tried deleting cache and several other things as well, but the behaviour did not change.
Only by opening a private tab, the entry fields for destination and date are empty. I ask: why? Is any information stored beyond cookies? I'm also sure that the site is not visited while getting in a logged-in state.

Is anybody able to explain this?