Why does my Macbook automatically open a browser Window at Starbucks? When I open my laptop at Starbucks a Chrome-window is automatically opened. It shows the login-page that allows me to log on to BT OpenZone for free Starbucks-wifi. 

What kind of mechanism is used to achieve this? After all I don't get the same effect with my Ubuntu-computer or my Android phone.
This is a new feature of OS X Lion.
Lion automatically opens a web browser window when it detects that you need to agree to terms and conditions or log in to use the Internet.

It's worth mentioning that the window isn't actually Google Chrome, but an operating system window that includes a WebKit-based browser.