Android App - need to get help checking status

Hello together! I need your help in detecting online status of a website. If it is online, the running app (which is already developed), have to give an alert, if the website is not longer online, the app needs to check every 10 seconds (over Intent Service) that the site goes online or not. In standby status of the phone, it works good but not in the non-standby mode (after pushing the ON/OFF button of the phone to go into black screen).