Why do scroll bars disappear?

[rowanbradley]

Who was the incompetent UI "expert" at MS who decided that scroll bars (e.g. in IE) should hide themselves after a few seconds and only reappear if you mouse over them? It is surely a given in UI design that users should be able to see on screen the things they can do? Is there any way I can turn this unwanted behaviour off?

Thanks - Rowan