It's one of those in-between places where it goes both ways really - since our FAQ mentions:
If your question generally covers … Browsers and their features relating to the use of a web application (Greasemonkey scripts for a web application, etc.)
then it's OK for us. While Super User does indeed accept questions on Web browsers / desktop applications, provided they aren't product recommendations.
I've migrated to Super User - and in general, Web Apps deals more with how do I get x done in web apps y(with the addition of using extension) - but Super User focuses more on getting things done with the browser/extension, regardless of the web app.