In Magento version 1.9.1.0, we got the error when we create order, invoice, register the user it display the blank page. On register page, user is registered at back end but I didn’t get the new user email.

Solution:

You must have to latest version php 5.4 or greater than.

Magento is using the pealog_emogrifier function used in mail

If you comment this function from the following file
app\code\core\Mage\Core\Model\Email\Template\Abstract.php

Function:

Replace the code with below code: