Through a service of some kind (internal or external), your website can be accessed every few moments to keep it alive in IIS (in memory). If the main domain is used in such a service, going to yoursite.com, you will see the traffic in your DNN logs. Since such a service can come to your site every 10 to 15 minutes, that is alot of useless data in the DNN logs.
If the service is going to the keepalive.aspx page.... yoursite.com/keepalive.aspx , the traffic is not shown in the DNN log.
If you are looking for a keep alive service, I do offer one.