[jeffgrant]

And Ed is correct about the DNS... when an ISP queries your DNS server, more often than not they cache the value in their local lookup, and will hold it there for a few days before going and checking it against your DNS server again.

They are supposed to follow something called the TTL (time to live) that determines how long that value should stay in their cache.

Typically, DNS service providers set this value (by default) at 1-3 days.

Personally, I set it to 1 hour, as I'd rather get a crap-load of DNS lookups than wait that long.

But, like I said, there are a TON of DNS servers that ISP's have their clients use that do NOT follow the TTL settings.

So, that means that while some clients might see your site almost immediately (either they're doing their first DNS resolution on your site, or their ISP actually follows the TTL settings), I can guarantee you that others are not, and it will be days before the worst cases do.