IE10 stop scroll bar from appearing over content and disappearing

There is a custom vendor-prefixed CSS property to set:

html {
   -ms-overflow-style: scrollbar;
}

Other options include auto, none, scrollbar, and -ms-autohiding-scrollbar. The latter causes the behavior you’re experiencing.

An excerpt from the MSDN documentation, specifically the abovementioned scrollbar value:

Indicates the element displays a classic scrollbar-type control when its content overflows.

Unlike -ms-autohiding-scrollbar, scrollbars on elements with the -ms-overflow-style property set to scrollbar always appear on the screen and do not fade out when the element is inactive.