CSS support in email client is limited and worse than IE6. For example, background image is not support by outlook 2007/10, Windows Live Hotmail and Gmail. So, you need to know what’s supported.
Keep the Design Simple
Forget all your best practices for CSS
Use tables for layout : Because clients like Gmail and Outlook 2007 have poor support for float, margin and padding, you’ll need to use tables as the framework of your email. div structure layout not support in all email client.
Set the width in each cell, not the table
Use a container table for body background colors
Do not use external style sheets many email services cut everything above the body tag.
Provide alt text for all images.
Declare BOTH height and width parameters for images.
write a general portrait of each elements .