Knowledgebase
How to enable/disable SEF URLs in Magento
In order to enable or disable Magento's built-in Search Engine Optimization for your store's URLs, you need to log in to the Magento admin panel and go to System > Web (on the left menu) > Search Engines Optimization.
There is only one setting in this menu called Use Web Server Rewrites. Setting this to Yes will enable SEF URLs in your Magento store. If you set this to No, your store will not use Search Engine Friendly URLs.