cnnmobile.com viewport width 320px, even though there is no meta viewport tag

iPhone seems to render cnnmobile.com with a viewport width of 320px, even though the site doesn't have a meta viewport tag. I would expect it to be rendered using the default width of 980px. How come?

http://dl.dropbox.com/u/41764/pos开发者_运维问答ts/Screen%20shot%202010-08-31%20at%2012.34.41.png