Magento Compiler - Quick Start Guidev
if you want to get even more speed from your Magento store then have a look at the Compilation feature, in SYSTEM > TOOLS > Compilation.
DO NOT click “Enable” until you have first clicked the “Run Compilation Process” button if you do your site will not load. If this happens via FTP click to Includes/Config.php which is in the root of your Magento webspace.
Then comment out (add a ## to the front of the line) these lines:
define('COMPILER_INCLUDE_PATH',dirname(__FILE__).DIRECTORY_SEPARATOR.'src'); define('COMPILER_COLLECT_PATH', dirname(__FILE__).DIRECTORY_SEPARATOR.'stat');
To use the compilation feature, first click the “Run Compilation Process” button so that it can compile the files and then automatically enable it.
BEFORE you install any extensions you MUST disable the compilation process, or you will get errors and site down problems.