Exception printing is disabled by default for security reasons
Mostly for magento sites you face following error.
Error log record number: XXXXXXXXXXXXXXX
In this case you need to check following steps.
Go to folder errors at magento root and Rename local.xml.sample to local.xml after this change you can see few more errors.
then Open magento/lib/Zend/Cache/Backend/File.php
protected $_options = array( 'cache_dir' => 'null',
and replace it with
protected $_options = array( 'cache_dir' => 'tmp',
Final step is to create a tmp folder on your magento root folderDOWNLOAD SOLUTION HERE