If you mean the blockchain.info site, it's owned by a party completely unaffiliated with Bitcoin. It's a private site with a block explorer and a wallet. If it goes down, well that's going to be problematic for its users.

If you mean the actual Bitcoin blockchain, it's not a website and is instead hosted by multiple people running nodes. It's why Bitcoin is a peer-to-peer currency. One or two going down wouldn't be a problem, and every single one going down is almost completely impossible.