How to inspect your webpage’s CSS using Web Inspector or similar built-in tools within your browser (Firefox, Chrome, Safari, or for IE use Firebug).

Quick Tip: Insert dynamically generated placeholder images within email templates and landing pages
Insert dynamically generated placeholder images within your email templates and landing pages simply by inserting a source link. Your source link will define your desired placeholder image size, and the image will render automatically to the correct size within your content.