If you are using Dreamweaver to create your 'Custom HTML' campaigns, you need to turn off the option to use CSS. (Cascading Style Sheets) All major ISPs strip the CSS and exclude it from e-mail resulting in poor design and invalid HTML.
To turn off the CSS, follow these instructions:(Macromedia Dreamweaver)
1. Open Dreamweaver
2. Edit > Preferences (Crtl+U)
3. Uncheck "Use CSS instead of HTML tags"
