On https://webapps.stackexchange.com/, I once asked whether it was possible to open a file from the desktop using a context menu, and load it in a web browser using a web application such as pixlr. I thought it was an interesting question, but the question was closed as off-topic. It appears that questions of this nature are not allowed on either superuser.com or webapps.stackexchange.com.
Questions about "desktop software" are considered to be off-topic on https://webapps.stackexchange.com/, while questions about "websites or web services like Facebook, Twitter, and WordPress" are considered off-topic on http://superuser.com. In that case, where should I post questions about applications that don't fit neatly into either of these categories? I'm not sure whether my question was a "web application question", a "desktop application question", or somewhere between the two.
It's not always easy to choose the right Stack Exchange site for a given question, given the intricacy of the inclusion/exclusion rules that are applied to each site. Is it possible for an application to be both a "web application" and a "desktop application" at the same time, or is there no possibility for overlap at all? If I ask how to "open a file with a web application using a context menu on the desktop", then I'm not sure if it's even possible to put it into either category.