Auto-scroll is when pages are automatically loaded as the reader scrolls. It will keep doing this so you don't have to keep clicking the next button. Some themes have this feature and some don't.
An example site: http://samago.tumblr.com/
After downloading this site, at the bottom of the first page, you will only see a small square with the text "The End". The auto-scroll does work if you browse the live site using the browser in OE.
The only way to partially navigate sites like this is to use the archive feature of the site and go day-by-day... but only for the first page of the archive (like the first page of the site).
I did enable the "Evaluate scripts calculations" in the Parse section of that site's properties to see if that would fix the problem but it didn't make a difference.