I wish to check some parameters before loading a webpage or publish content. If parameter complement a particular value i wish to try taking some action like running some javascript, notifying customers, securing contents etc.

I'd rather not edit theme. Please suggest some hook or snippet to get it done individually rather than modifying existig code.

You can utilize the_publish action hook or filters such as the_content or even thename, it is dependent on which for you to do.

The entire listing of all hooks: http://adambrown.info/p/wp_hooks/hook

About while usingpublish hook: http://wordpress.org/support/topic/how-to-use-the_post-action-hook