the scheme and hostname is case-insensitive.
the path, file name, query string and fragment identifier are all case-sensitive.
you should name all your files and directories with lowercase and no spaces.

Agree with phranque. I made this mistake 10 years ago (using mixed case) and paid for it in broken links over the years until I finally realized it was a problem and built-in some re-direct rules to fix it.

I got caught with the very first site I ever built and didn't ensure that the case in the links matched the file names. Worked fine when I tested it on Windows and couldn't understand why it was failing after I uploaded it. Maybe I should have taken it as a warning and abandoned the frame based design then, it took me several weeks to learn better.

And if you need to break up directory name or file name to make the URI easier to follow, do so with a hyphen. Underscores are pretty common, but you can't see them in a link. Hyphens are obvious.

www.example.com/easy-read/easy-read.html

If this is the case that
the scheme and hostname is case-insensitive.
the path, file name, query string and fragment identifier are all case-sensitive. , then why is

http://www.example.co.uk/properties/propertylist.php

opening and this http://www.example.co.uk/properties/Propertylist.php also opening fine?

[edited by: bill at 7:38 am (utc) on Oct. 30, 2009]
[edit reason] No URLs or links to personal sites. Use example.com [/edit]

Sounds like a question for a server expert. I just replaced a page with a copy where I put the first letter uppercase and got the expected 404. Put the original page back up, and back in business.

To satisfy my curiosity: Could there be two separate files with different names on this server, propertylist.php and Propertylist.php, with identical contents? Or a mod_rewrite?
But, is it necessary for Angelina to post real URL:s here, twice? I support the WebmasterWorld custom.