In short, a file URL takes the form of:
file://localhost/absolute/path/to/file [ok]
or you can omit the host (but not the slash):
file:///absolute/path/to/file [ok]
but not this:
file://file_at_current_dir [no way]
nor this:
file://./file_at_current_dir [no way]
I just confirmed that via Python's urllib2.urlopen()
More detail from http://en.wikipedia.org/wiki/File_URI_scheme:
"file:///foo.txt" is okay, while "file://foo.txt" is not,
although some interpreters manage to handle the latter
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