This application will keep running in background. when a user tries to access a site from a browser( chrome, firefox, opera mini etc) on mobile device. the url will be validated from an online database. if the url is not present in database then user will be able to access it as it is else user will be redirected to page 404. I am not sure if the application will have access to verify a url which is access from a different application. rooting the phone is not an option for me.