Word 2007 HTML and CSS Rendering Capabilities in Outlook 2007

HTML structures are very different rendering system between web mail system email (Gmail)and Outlook based email system. When we make email blast newsletter, we realized those differences. Outlook understands only certain HTML code tags. Following reference article show full chart of HTML specification

Introduction to HTML Parsing and Rendering in Outlook 2007

Microsoft Office Outlook 2007 uses the HTML parsing and rendering engine from Microsoft Office Word 2007 to display HTML message bodies. The same HTML and cascading style sheets (CSS) support available in Word 2007 is available in Outlook 2007.
This article provides reference documentation related to supported and unsupported HTML elements, attributes, and cascading style sheets properties.
Word 2007 HTML and CSS Rendering Capabilities in Outlook 2007 (Part 2 of 2) provides detailed instructions about how to install and use the Outlook HTML and CSS Validator tool.
The Outlook HTML and CSS Validator tool helps you to validate HTML and cascading style sheets grammar using some of the most popular Web development tools, such as Microsoft Office SharePoint Designer 2007, Microsoft Expression Web Designer 2007, Microsoft Visual Studio 2005, Macromedia Dreamweaver MX 2004, and Macromedia Dreamweaver 8.
These articles and accompanying tools are provided for your use and can help you to better understand the new capabilities offered with the switch to the Word 2007 HTML parsing and rendering engine. This information can help you with the generation of e-mail newsletters or other complex HTML documents.

Supported HTML Elements, Attributes, and Cascading Style Sheet Properties

Word 2007 supports a subset of the standard HTML 4.01 specification and of the Internet Explorer 6.0 HTML specification. Word 2007 also supports a subset of the standard Cascading Stylesheet Specification, Level 1. Word 2007 uses HTML elements that support a subset of the Word 2007 cascading style sheets properties. This article categorizes the Word 2007 supported cascading style sheets properties as follows:

FULL. The subset of the standard cascading style sheet 1.0 specification fully supported by Word. Note that Word 2007 also uses HTML elements that support a subset of the Word 2007 cascading style sheets properties.

COREEXTENDED. Two HTML elements that support a subset of the cascading style sheets properties are called out: DIV and P. DIV and P support a subset of Word 2007–supported cascading style sheet and are defined in this article by the term COREEXTENDED.

CORE. SPAN supports a smaller subset of Word 2007–supported cascading style sheets, defined by the term CORE.

Reference Site Link below:
http://msdn.microsoft.com/en-us/library/aa338201.aspx