Some networks, often public ones, use captive portals to ask the user to consent with it's terms of agreement. Browsers on desktop are aware of such portals, often by checking access to sites like http://detectportal.firefox.com and see if it's captured by a portal, but Angelfish isn't. It'll just fail to load any webpage without informing the user why this is.
Ideally it uses pages like http://detectportal.firefox.com (or some KDE-specific non-SSL accessible page) to detect the user needs to navigate to a portal and prompt the user to do so.