This is mostly a bug report (unless I've overlooked something obvious), as I couldn't find a better place to report it. When using the Firefox browser on my Android phone, I am unable to access my Dropbox files (via https://www.dropbox.com/home ), because almost immediately I get a full-screen pop-up offering a free trial - with no way to dismiss/cancel it:
It looks very similar to the pop-up I get on my desktop computer, but with that I can click outside the pop-up to dismiss/cancel it. So this seems like a bug with the Dropbox website.