the subtleties of browser differences
A few people reported to me that with Microsoft's new "Edge" browser (which they
force upon you when installing/upgrading to Windows 10), the inner lines of cages are
no longer visible.
With some effort I upgraded an old dinky netbook from Windows 7 to 10, and was able to test.
It turns out that "Edge" interprets certain empty CSS fields differently from other browsers.
This should be fixed now...