[rmc]

I would guess "website number" does mean the web address. My 50 year old landlady gave me her "email number".

I'd also saw Patrick is talking about 2 different browsers on the same computer. "don't talk to each other" probably means they don't share cookies. If the user logs into one website with one browser, then the other browser doesn't become aware of each other. Clearly the 2 browsers don't talk to each other.

[chc]

I think "website number" must be a username or password of some kind. You wouldn't use a different address to get to BCC depending on your ISP.