Just suprnova.cc website itself, or some specific pool? Not sure about hidden miner, but the front end of suprnova pools (at least ZEC and HUSH) is based on some fancy MPOS thing, that is nice, but... if I leave it open on hidden tab for some time, then click the tab back, the graphs trying to show many things and screen starts lagging a bit for a while. Also my phone (Android) had hard times to render the screen if the tab was opened for longer time.