This is the message I got from them:
We found that the experience your app provides is not sufficiently different from a web browsing experience, as
From that message (and since you didn't give a description of the app at all), it seems like you just made an app that encapsulated an UIWebView to load an specific page, since you can do that via Safari, they reject apps like that.
You can:
Make the app fetch the data from the web server, BUT, display it with native controls (with UITableViews, UIButtons, UIImages, etc). This would require quite a bit amount of work.
Drop the app and tell the users, on your site, that they can add that website as a web clip on their phones.