That was WM, not me. He'd know as I don't use FF or Chrome unless I really need to.
I have seen the message from time to time but, as WM says, this is simply saying that you're not using SSL (HTTPS), to secure your password.
The reason it is saying this is that anyone on the network, monitoring traffic to the server you are trying to log into, will see your password in plain text. So it depends on how important that login is.
For instance if you are using a mail address and password you use for something important, you should not use it on a site which is http only. If it is
noddy@toytown.com with the password GoToHell, it's not likely that you will care...