Every horizontal pixel column represents a sample of a cumulated orderbook. Whenever color is lighter it means theres relative high orders in that price range. I think its pretty unique to my site although i have seen samples out there from regular stock market used investing fraud. I still want to print date and hours 0-24 on x axis and price on y axis but havent gotten around it yest. Performance was a problem but should be fixed now. Glad you like it!