Magento Admin panel login not working in localhost

Step 1: Copy varien.php file from app\code\core\Mage\Core\Model\Session\Abstract folder

Step 2: Paste into app\code\local\Mage\Core\Model\Session\Abstract folder. Before you paste the file you need to create the folders as specified in this path such as \Mage\Core\Model\Session\Abstract.

Step3: Open varien.php in your favorite editor.

Step4: Find line no 96 and the code will be like

if (isset($cookieParams['domain'])) {

$cookieParams['domain'] = $cookie->getDomain();

}

     and replace with

if ((isset($cookieParams['domain'])) && !in_array("127.0.0.1", self::getValidatorData())) {

$cookieParams['domain'] = $cookie->getDomain();

}

Step 5: That’s it. Now you will be able to login Magento admin panel.