I have it running on an Internet page as well as my local development system. If you site is already indexed by Google, the CSE will display results from your site. In addition, you can configure the CSE to display results from all domains, some domains, or only your domain. The results can be formatted and the script can be nicely used in your code so that the results page integrates perfectly with your theme. Alternatively, if you prefer, you can have the results page look just like google's result page. Its 100% customizable.