I think you can also just keep sending html. Send a page with page2.png at the bottom and keep the connection open. This is a sentinel image to detect scrolling

I think you can also just keep sending html. Send a page with page2.png at the bottom and keep the connection open. This is a sentinel image to detect scrolling — when page2.png is requested, use this as a command to tell the server to start sending html for page 2 on the original connection, which would have page3.png at the bottom.