Thanks for the answers. So the 100% width means that on a desktop it will fill the monitor and on a mobile phone it will do the same. Even though the email looks exactly the same, it just fits the width of the device. Is that right?
I assume there is a way to keep the email from being 19 inches wide on desktop monitors.
FYI : I am looking for a one column, really great looking, modern, professional fluid email template that I can use in Aweber easily.