Invalid form key

#0 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/code/core/Mage/Checkout/controllers/CartController.php(609): Mage::throwException('Invalid form ke...')
#1 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Checkout_CartController->ajaxDeleteAction()
#2 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action->dispatch('ajaxDelete')
#3 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/code/core/Mage/Core/Controller/Varien/Front.php(172): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#4 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/code/core/Mage/Core/Model/App.php(354): Mage_Core_Controller_Varien_Front->dispatch()
#5 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/app/Mage.php(692): Mage_Core_Model_App->run(Array)
#6 /data/sites/cityfurniture-20140701-1400/cityfurniture.com/index.php(90): Mage::run('default', 'store')
#7 {main}