Retired Documentation: You are using the documentation for version 1.7.3 which was retired in 2013. Go here for the latest version documentation or check here for your available upgrades to the latest version.
Update Notes for Version 1.6.5
Strict URLs
During the update, the new Strict URL preference is either enabled or disabled depending on your Site's "404 Page" setting. If you have a "404 Page" set, then Strict URLs will be enabled for the site, to provide the closest match to existing behavior. If you do not have a "404 Page" set, then Strict URLs will be disabled.
jQuery for the Control Panel Extension
ExpressionEngine 1.6.5 includes a new control panel extension, "jQuery for the Control Panel". The language file for this extension will already be updated if you have followed the instructions on updating your language folder, but you will need to upload the ext.cp_jquery.php file from the download to your /system/extensions/ folder.