If you do not see the symbol,
then stop, and look for a 
phone number for the 
company.  It is far safer to give your credit card information over the phone than over an unsecure link on the World Wide Web.  

The same holds true for other personal information, whether it is a name, address, etc.  Bank account information should be considered as vulnerable as credit cards.  Guard yourself, and you will not fall victim to fraud.