The owner of the site should encrypt the login page with HTTPS. otherwise you will get a "not secure connection warning"- both firefox and google chrome do this 'now' for safety reasons. An Attacker could see your password and other personal information (and steal it) because the information is not encrypted as its passing thru servers, networks, and what not.
This is another reason why you should use different passwords for all of your accounts. (my main email account has a different password than my account on here)... If the site is secure for transmitting personal information, you'll see an "HTTPS" in front of the site URL. (If you're doing online shopping, don't enter credit card info on sites that don't have this)