Often used API functions

$modulepath= drupal_get_path('module', 'nameofmodule');
drupal_add_css($modulepath. '/cssname.css');
drupal_add_js($modulepateh. '/jsname.css');

Drupal javascript namespace
Drupal.t()
Drupal.checkPlain()

Drupla php has no namespace???
t()
l()
check_plain()