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 ExpressionEngine 3.
ExpressionEngine has a feature that allows you to send a "ping" to the ExpressionEngine.com servers. This notifies ExpressionEngine that you updated your site and will allow you to be listed in a "recently updated sites" list.
Enabling this feature is simple and only requires a few steps.
In the Control Panel, go to your General Configuration page. In the License Number setting you need to enter your ExpressionEngine License Number. This is a four-segment number that you received with your ExpressionEngine purchase receipt email. It looks similar to this:
If you no longer have your ExpressionEngine License Number, then you may get another copy of your license number by going to the Download Area of the ExpressionEngine site and accessing the "Purchase History" for your product.
In the Default Ping Preferences section of your Control Panel, you will want to add an entry for the ExpressionEngine ping server:
You may also wish to make sure that the ping server is listed in your individual list available under My Account.
Once the Ping Server has been added, it will appear in your list of available servers whenever you create a new entry on the Publish page.