coinmarketcap.com is used by almost every Crypto Trader, it gives a quick view of the state of all coins, and tokens in the crypto world.
So what happened yesterday, when all the prices fell together, most people thought a crash was happening.
coinmarketcap decided to remove South Korean Exchanges from their stat calculations, the reason is that the prices in the crypto crazy country of South Korea do not actually relate to the rest of the world.
The exchanges removed are Korbit, Coinone and Bithumb.
They still appear on coimarketcap but their prices are not used to work out average prices.
It means that the prices now shown are truer to life, without using the crazy prices from South Korea, where the spread on Bitcoin can be $5,000 (difference between buy and sell price).
It seems a wise move to me, but would have preferred an announcement that it was about to happen, instead of just doing it.