CSS: The Definitive Guide
Provides you with a comprehensive guide to CSS implementation, along with a thorough review of all aspects of CSS 2.1. Updated to cover Internet Explorer 7, Microsoft's vastly improved browser, this new edition includes content on positioning, text wrapping (nowrap), lists and generated content, table layout, user interface, paged media, and more.
Set different values for an element based on browser (specifically, how the browser interprets the CSS). Definitions must be in order as shown below because newer definitions override existing.
The first setting will apply to all browsers.
The second setting (using a pound symbol, #) will only apply to Microsoft Internet Explorer.
The third setting (an underscore, _ ) will only apply to IE browsers 6.0 and older.