Place downloaded and custom modules that extend your site functionality beyond Drupal core in this directory to ensure clean separation from core modules and to facilitate safe, self-contained code updates. Contributed modules from the Drupal community may be downloaded at http://drupal.org/project/modules. It is safe to organize modules into subdirectories, such as "contrib" for contributed modules, and "custom" for custom modules. Note that if you move a module to a subdirectory after it has been enabled, you may need to clear the Drupal cache so that it can be found. In multisite configuration, modules found in this directory are available to all sites. Alternatively, the sites/your_site_name/modules directory pattern may be used to restrict modules to a specific site instance. Refer to the "Developing for Drupal" section of the README.txt in the Drupal root directory for further information on extending Drupal with custom modules.