Hi Anna,
With these steps you solve your problem and remove this error.
- Navigate to the "errors" folder
- Change local.xml.sample to local.xml
- You should now see a new list of crazy errors all over the Magento page - this is okay.
- Open magento/lib/Zend/Cache/Backend/File.php and look for:
protected $_options = array( 'cache_dir' => 'null',
- Change it to:
protected $_options = array( 'cache_dir' => 'tmp/',
- Save it.
- Now the final step is to go create a tmp folder in the root Magento folder.
That's it 