Open
magento/app/code/core/Mage/Core/Model/Session/Abstract/varien.php

change:

session_set_cookie_params(
$this->getCookie()->getLifetime(),
$this->getCookie()->getPath()
$this->getCookie()->getDomain(),
$this->getCookie()->isSecure(),
$this->getCookie()->getHttponly()
);

to:

// set session cookie params
session_set_cookie_params(
$this->getCookie()->getLifetime(),
$this->getCookie()->getPath()
//$this->getCookie()->getDomain(),
//$this->getCookie()->isSecure(),
//$this->getCookie()->getHttponly()
);

Or Open

magento/app/code/core/Mage/Core/Model/Session/Abstract/varien.php

delete code

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