g1smd - 10:12 am on Feb 22, 2013 (gmt 0) [edited by: g1smd at 10:25 am (utc) on Feb 22, 2013]
Never use underscores or spaces in URLs.
If you need to split and use something other than a hyphen, go read the HTTP/1.1 specification and look specifically at the section that lists the valid characters that can be used in the path part of the URL in an unencoded form. There's at least comma, tilde, plus, and a few others to choose from.
[edited by: g1smd at 10:25 am (utc) on Feb 22, 2013]