Compilation is a funny thing. For the most part, it seems to be officially deprecated: http://magento.stackexchange.com/questions/12996/when-should-i-use-the-magento-compiler If you've ever managed to install an extension or make serious code changes without disabling Magento's compilation, you may have noticed some adverse affects including blank web pages on both the front and back of your instance. Below are 3 ways to disable compilation even if you can't access your admin panel.
// First Option: Via Magento's admin section Navigate to System then Tools then Compilation page and click on Disable button Navigate to System then Cache Management screen and use Flush Cache button. // Second Option: Via FTP or SFTP, by editing the includes/config.php file Edit includes/config.php around line 28 and uncomment the first line then comment out the second: define('COMPILER_INCLUDE_PATH', dirname(__FILE__).DIRECTORY_SEPARATOR.'src'); #define('COMPILER_COLLECT_PATH', dirname(__FILE__).DIRECTORY_SEPARATOR.'stat'); You can also try commenting out both lines if necessary which restores the file to factory state. // Third Option: Via SSH ("shell") php -f shell/compiler.php -- disable php -f shell/compiler.php -- clear // More regarding SSH # php -f shell/compiler.php -- state Compiler Status: Disabled Compilation State: Not Compiled Collected Files Count: 0 Compiled Scopes Count: 0 // Finally run this rm -rf var/cache/* var/session/*