The problem with many software applications is you can't make them your own. With Drupal, however, you have the option to override how Drupal does things. From altering a form to customizing the way your pages are displayed, Drupal provides options.
The concept of overriding something in Drupal can be made reality in several ways: Drupal's APIs, theme overrides, as well as overriding default configurations in modules. Whatever it is you need to do, the number one rule you should endeavor to follow is: don't hack the core (or a contributed module). Don't open the code files in Drupal and change them to meet your needs. There are better ways.
In this tutorial, we will focus on overriding themes.
Read more ...