Drupal's theme layer, and the themes that use it, are responsible for the look and feel of a Drupal web site. Good themes consist of all the same elements that you would find on any reputable web site, including standards-compliant XHTML markup, CSS, and JavaScript. How it all comes together is what is so special and what makes Drupal themes so flexible and powerful.

Drupal themes can be as simple or as complex as you need them to be. Themes have the final say and ultimate control over almost every aspect of each page. Like Drupal itself, themes are flexible and powerful. Admittedly, taking full advantage of Drupal's theme layer means overcoming a rather steep learning curve, and without a general understanding of what's going on under the hood, it is easy to make mistakes early on.

In this chapter, you will learn about the basic aspects of Drupal's theme layer. You'll learn how to go about making customizations and changes in a sustainable way and best practices for common tasks. You will be well on your way to creating flexible and sustainable custom Drupal themes in no time! The next chapter will build on this one and will cover the more advanced intricacies of Drupal themes.

Some of the examples you'll find throughout this chapter and the next can be found in the DGD7 theme. It's available at for download if you'd like to follow along.