Not to be too obvious, but on occasion, when I have my browser window sized in a certain way, the ‘scroll’ bar is missing from views, both the up/down on the right and the right/left on the bottom. Try shrinking your browser window and see if these bars shows up.
Also, unlike some browsers, these tabs have to be dragged around, rather than clicking on an open space and having the page scroll jump to that space in the total page space.