Open any website that contains a video (live doesn't work)
Long press the video player box on the browser page (normally a black box with play icon)
You will see a pop up menu Open, Open in a new window etc.
Press Open in a new window
It will give you an option to choose your media player (I choose avia media plyer)
then cast to Chromecast
Tried this website einthusan com
Let me know if you find any other website
Some of you may know this trick already but thought of sharing this with everyone.