It's probably specifically penalizing anything matching /https?:\/\/0/ because you can specify an IP address using hex or octal in most common browsers.
hex: http://0xD83AC02E
octal: http://033016540056
That's my guess, at any rate.
hex: http://0xD83AC02E
octal: http://033016540056
That's my guess, at any rate.
Edit: You can usually find out what they mean by going to https://www.google.com/doodles