How to watch multiple streams at the same time easier? (HELP ME)

Ok so i was checking reddit with my phone and i found this thread about watching multiple streams at the same time. I don't know how it works but there was this site where i was supposed to drag the stream to a little box and it would make it fit your screen better or something. And now i came to my computer and i cant find the thread anymore?! Can someone tell me where to find this site or thread? Thank you for anyone who can help me with this!