Trace why magento url is being redirected to 404 page

As soon as you open any magento based URL then following three thigs occur 1.Read the required controller and controller is dispatched based on URL routing 2.If your module name is mage_cms writter from module’s etc/config.xml then your contller will be called from following location ‘moduleName/controllers/controller/’ if no action is defined then IndexController.php will get(…)