CSS Support
“CSS Support” function filters the sourcecode of the email to check whether it contains any Cascading Style Sheet (CSS) code that is not supported by one of the email clients “css_support.csv”. If it finds an unsupported style – it indicates the style and email client that will not be able to render it properly. CampaignMonitor has produced a Spreadsheet indicating all style sheets and what email clients are unable to render them. This Spreadsheet was adapted for this function, as it has proven to be extremely popular among the email marketing experts.
http://www.campaignmonitor.com/blog/archives/2006/03/a_guide_to_css_support_in_emai.html
