If you use php applications in your website (most content management systems) you may have a problem with PHPSESSID. PHPSESSID is the PHP session identifier. You can sometime see this in the url data while using the PHP applications.
This session ID is not something you really want to be showing your users for aesthetic reasons but also security reasons.
There are a number of different ways to hide them from surfers, but some methods do not work in certain server environment. If the web server doesn’t allow you to configure PHP settings you will have to find a way around. The link below details how to remove the session ID in a number of ways. The article is oriented toward Drupal, but should give you some insight to how to do this with other web applications.