Not even the network carrier should be able to tell the duration of a web page visit. Only the browser (or tracking javascript) could record this, but that's still dubious. I've had some browser tabs open on my phone for months... but that doesn't mean I've been constantly looking at them for months. I doubt Android keeps a big database of every page you visit and how long it takes you to close the page or navigate away. I guess Google Analytics might have some of that data, but only for sites that use GA.