Adding special characters in URL

Hi,

I saw this URL http://www.parashift.com/c++-faq-lite/abcs.html

And i have noticed that WordPress doesn’t allow some special characters in URL like + character. Howcome wordpress doesn’t allow this and how can i tweak wordpress to allow it since it is possible from this URL http://www.parashift.com/c++-faq-lite/abcs.html