Div styles not working in Outlook Emails
Here's the DIV properties compatibility table (taken from www.campaignmonitor.com, see LiamB answer):
Client Float Position Margin Width
Outlook 2003 / Express Yes Yes Yes Yes
Windows Live Hotmail Yes No Yes Yes
Yahoo! Mail Yes No Yes Yes
Outlook 2007 / 2010 No No Yes No
iPhone Yes Yes Yes Yes
Gmail Yes No Yes Yes
Apple Mail 4 Yes Yes Yes Yes
Lotus Notes 6.5 & 7 No No No No
Float width and position CSS styles applied to div's do not work in Outlook.
- Link Now Dead - https://www.campaignmonitor.com/blog/post/3472/div-tags-in-html-email-newsletters/ (See table half way down)
This is the primary reason while Tables are still used so heavily in Emails.
I would suggest you to make basic html structure using a table tag.
You can then use "div" tags insde "td" tags.
Email templates are a pain because most of the cool stuf doesn't work :D