Manageable CSS in your email templates0
Inline CSS styles are the most compatible way of using CSS within your email newsletter templates, but it can get messy very quickly.
Alex Dunae’s free Premailer tool is the answer. It’s been available for a while, but not everyone’s aware of it, and it really is fantastic.
It means you can keep your CSS in a nice neat block at the top of your HTML code, then just run the file through his tool before you send.
I’ve seen this also fix a lot of compatibility problems with email templates as well, especially for Gmail.