Naming convention

I don’t know if it’s the correct mailing list for this question. 

Anyway I would like to know if there is an international convention for
the URI naming.

I mean, could I use uppercase and lowercase characters
(http://www.domain.com/TEST/Tesh.html.....)?

I’m sure we can not but I cannot find any rules for that.

 

Any ideas or links that could help me ?

Many thanks.