Some IE/Windows compatibility issues I noticed: file://foo/bar should be treated as UNC like IE. UNC file URLs copied from IE will fail to load in Safari. Links on web pages of the form "\\foo\bar" should be treated as absolute UNC paths to file://foo/bar. Relative links of the form "/hello" on pages loaded from a UNC base path of the form "file://foo/bar/" should be "file://foo/hello" rather than "file:/hello" A more comprehensive set of tests for IE-compatible UNC file path handling is in the CanonicalizeFileURL test in: http://code.google.com/p/google-url/source/browse/trunk/src/url_canon_unittest.cc