Google's server is case sensitive

or the URL's on Google's server

[sdani]

Try out the Adword's URL with an upper case A:

[google.com...]

[gertrijs]

Most (*nix) servers are case sensitive. As far as I know, only Windows based servers are not.

Gert

[victor]

All URLs are case sensitive (except for the domain name part -- try WWW.GOOGLE.COM/ads )

A UNIX file system is case sensitive, while a WIN one is not. But that does not directly related to URLs. A URL is not a file name.

A URL like:
[google.com...]
may result in you being served a file called...

/home/stuff/stuff/stuff/ADS/home/index.HTML
or
c:\stuff\stuff\stuff\ADS\home\index.HTML

...you'd never know what the actual file is.

So URLs map to file names (with a one-to-many mapping in the case of cloaking or geo-targetting, etc).

It's that mapping that Google is doing in a case-sensitive manner. I guess they are just too big to bother being user-friendly any more.