You are looking at an email in a Web Browser
When looking at a Preview of an Email Message, you are letting your web browser (IE, Firefox, Safari, Chrome, etc.) render the HTML of the message.
Web browsers will present the view in a way that is optimum for web browsing. Often times, this view is different than what you would see when viewing in a dedicated application for email reading (e.g. Outlook, Gmail, mobile mail, etc).
Browsers tend to render HTML differently than email applications. As a result, the "Preview" version of the email may look different than when it is actually received in your message inbox.
Don't Rely on a "Web View" - Use an actual Email Client
The best method for testing email message formatting, is to send yourself Proof messages to as many different email clients as possible. Additionally, users may want to consider previewing their emails with our Litmus Integration.
Keep in mind that HTML code is also rendered differently from email client to email client, so it will be difficult, if not impossible, to code an email so that it looks exactly the same across all platforms.