Enable PHP Error reporting in Magento : This is very important and a must for all magento front-end + back-end developers .By default magento disables the error reporting and if something goes wrong with it , you’ll see an error like this .
There has been an error processing your request
Exception printing is disabled by default for security reasons
The simple solution to enable the error reporting is , go to your magento index.php and add these lines
error_reporting(E_ALL | E_STRICT); ini_set('display_errors', 1);