If you enabled the Force SSL option, and you've become locked out of your website, follow these steps to restore the normal, non-ssl setting.
Step1: First you need to go to backend Joomla 3.1 folder to find and edit configuration.php file.
Step2: Once you have opened configuration.php file then find a line that looks similar to this "public $force_ssl = '2'". Please change this line to "public $force_ssl = '0'". That means "Force SSL" value should be changed from "2" or "1" to "0"