No, it´s not a mistake. You can really run a web server on your S60 mobile phone. Wheter you find it useful or not, that´s up to you.
Nevertheless, they have found some interest uses. Accesing calendar, contacts or SMS through the website the phone provides (and that includes sending SMS) are just the basic features. Sharing the pictures of you camera gallery and maintaining a mobile website like a blog with RSS support are some of the advanced features.
Beware, get an unlimited data plan or prepare to face the famous “carrier charges may apply”.
Link Mobile Web Server