URL with php extension or trailing slash not added in Firefox (v30.0, Linux Mint 16)

URL with php extension or trailing slash not added in Firefox (v30.0, Linux Mint 16)

I can add href:

http://www.facebook.com/sharer/index.html
and
http://www.facebook.com/sharer/

but not

http://www.facebook.com/sharer
or
http://www.facebook.com/sharer/sharer.php

Neither through .append() or attr("href", [URI])

Using jQuery 1.11.1