The browser won't allow to save passwords for websites running on localhost (e.g. as a developer) due to failed syntax check; it's expecting a valid domain name or IP address and suggesting to append ".com" to "localhost". Not a security thing, because I can save passwords for 127.0.0.1 just fine (since it's a valid IP). This is clearly a bug. The syntax checker must allow "localhost" as an exception for a proper domain name (which it is!)
