I've already said it in #2350, but as it's not exactly the same issue, I open a new one:

*There's no option in rightest drop-down menu responsible for closing a tab without deleting its content from disk (in other words: there is a "delete" option but not a "close" option)

*File-> Close and File->Quit do the same: they close the IDE...(I think former should close only active tab)

Tested on 1.6.1 and on 1.6.3