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