How to include jquery.js

Well, I just updated our company site then suddenly i have a error on one of my scripts written in jquery after a time searching for this problem i've noticed that jquery.js was not loaded.

Solution for this is creating a script.js inside your theme directory. Suppose you have a custom theme we will name as "custom_theme". inside your custom_name folder create a script.js file this way drupal will load this file as well as jquery.js

you can dig more about this in drupal http://drupal.org/node/243134