This post explains how to disable the Session ID in URLs of your Magento.
Magento adds a SID at the end of the URL by default.
Option 1 – Disable SID from Magento admin
Login to your Magento administration panel and Go to System->Configuration->Web tab.
Option 2 – Edit App.php file
In some cases using option 1 does not work and Magento overwrites your settings. To ensure SID is disabled, you need to manually edit Magento’s App.php file. Go to app/code/core/Mage/Core/Model folder on your server and open/download the App.php file.
Change $_useSessionInUrl value from “true” to “false“.
Note. This value is reset to its default “true” value when Magento is upgraded. Remember to change it back to “false”.