I cannot login into magento frontend

Go to template/customer/form/login.phtml and template/persistent/customer/form/login.phtml and under

add the following code in the login form

<input type="hidden" name="form_key" value="<?php echo Mage::getSingleton('core/session')->getFormKey(); ?>" />


If you are using the login form in different templates then you use add the form_key to the other parts as well.