Since a lot of people are confused, let me clarify what this change does. Currently, when you click on a bitcoin: URI
like this, your browser will open the client on your computer that is registered to the protocol. However, for security reasons, browsers won't let you register that protocol to a web-based client like blockchain.info because many protocols were made for a single application that resides on your computer, not as something that a webapp can also handle. Because protocols like "mailto:" are designed to be used by all kinds of applications, both on your computer and on the web, it is "whitelisted" so that a website can register itself as what should open when you click on the link. With this change, clicking a bitcoin: URI can be set up to load up blockchain.info's wallet, for example.
