If you manually enter the website address in your browser it will ensure that you are going to the desired website. Otherwise according to recent security issues that were discovered you will have no idea.
It is recommended that the site that you are intending to perform commerce with that you start your connection with a newly opened browser and manually enter the website address.
Never click on links inside an email or suspicious web site that leads to a commerce site. Never fill out a web form inside and email, and never fill out a web form that you did not request.