2.2.10 [CSS-Level2-2009] Section 11.1.1, Overflow: the 'overflow' property
scroll This value indicates that the content is clipped and that if the user agent uses a scrolling mechanism that is visible on the screen (such as a scroll bar or a panner), that mechanism should be displayed for a box whether or not any of its content is clipped. This avoids any problem with scrollbars appearing and disappearing in a dynamic environment. When this value is specified and the target medium is 'print', overflowing content may be printed.
Quirks Mode (All Versions)
Scroll bars do not appear when the container for a box with
the value of the overflow property set to
does not have a height or a width specified.
IE8 Mode (All Versions)
Margins are not accounted for scrolling when in overflow situations.