According to http://www.w3.org/TR/css3-values/#uris Parentheses, commas, whitespace characters, single quotes (') and double quotes (") appearing in a URI must be escaped with a backslash: '\(', '\)', '\,'. We unescape those escaped characters but the unescaping of \\ at the end of the url is broken. The following works url("http://digg.com/?\\abc") but this does not work url("http://digg.com/?\\") it never even tries to do a network request.
See also: bug 18604.
(In reply to comment #1) > See also: bug 18604. I closed bug 18604 as invalid.
Created attachment 166135 [details] test example - worksforme
the just attached test shows there is no problem with escaped backslash at end of url(), both in quoted and unquoted forms; verified (manually) that both perform network access on URL with single backslash at end (after unescape)
(In reply to comment #4) > the just attached test shows there is no problem with escaped backslash at end of url(), both in quoted and unquoted forms; verified (manually) that both perform network access on URL with single backslash at end (after unescape) tested in 537+ mac-mountainlion