Scroll Bars are he vertical bar to the right of the screen with little triangular arrows at the top and bottom AND the horizontal bar at the bottom of the screen with the little triangular arrows at the left and right side) these help you 'move around' a screen.
They only appear when the screen you are in is bigger than the current available area.
There is an intuitive problem with them in that if you push the 'up' arrow the page goes down (as you the user moves up the screen)
Back to the bit that mentioned scrollbars

Modularity
In Web graphic terms this refers to reusing graphics in different ways in order to save download time but provide interest by ordering them in different ways. Because the graphics are already in your computers buffer they dont have to be downloaded from the originating site but can be "recycled" from the buffer and used again and again.
See the Pirie Enterprises site for a look as well as this one.

Alternative Sequential stucture

This is where the user could be presented with an alternative to trying to guess correctly where to go next in the website by being taken on a guided tour with next page and previous page type navigation to take the random nature out of client navigation choices.

They would be told - If you dont know where to go next here is a structured way of visiting the site by going here* and then here* and then here* and finally over to the checkout to buy some stuff before you leave (we hope).