Chapter 12. Validation and Backward Compatibility

This final chapter discusses two related topics. It begins with a description of the use of W3C and other CSS-validation tools and techniques to ensure that your CSS designs create valid pages. Particularly, as you migrate existing table-centered designs to CSS, validation will be helpful in pointing out areas where you haven't quite lived up to CSS expectations.

The second part of the chapter focuses on some small changes you can make to valid CSS pages so that they will display as correctly as possible in older or incompatible browsers. It discusses using gateway pages and browser sniffers to route browsers to compatible pages, how to use the @import rule to avoid some potential pitfalls, and how to define a page's DOCTYPE property to gain more direct control over the rendering of that page.