Magento: Invalid form key. please refresh the page error

Magento Admin panel throws error Invalid form key. please refresh the page.  This issue happen through number of ways, so I will guide some points to sort out these.

• Completely clear the /var/session and /var/cache folder
• Clear your browser cache and cookies
• Update proper domain value in core_config_data table where path is web/cookie/cookie_domain
• Still your facing the issue, comment below line from app/code/core/Mage/Core/Model/Session/Abstract/Varien.php file line between 87 to 105

// session cookie params
$cookieParams = array(
    'lifetime' => $cookie->getLifetime(),
    'path'     => $cookie->getPath(),
    'domain'   => $cookie->getConfigDomain(),
    'secure'   => $cookie->isSecure(),
    'httponly' => $cookie->getHttponly()
);

if (!$cookieParams['httponly']) {
    unset($cookieParams['httponly']);
    if (!$cookieParams['secure']) {
        unset($cookieParams['secure']);
        if (!$cookieParams['domain']) {
            unset($cookieParams['domain']);
        }
    }
}