CSS, or Cascading Style Sheets, is a style sheet language that describes the presentation of a document written in Hypertext Markup Language (HTML) or Extensible Markup Language (XML). In other words, where HTML might define the basic elements of your email, CSS adds formatting, font color, background color, background images, and columns.
Use CSS to add the following to your HTML email templates:
Create beautiful email designs: Add color, font, columns, and styles to your emails.