The Element.clientWidth property is zero for elements with no CSS or inline layout boxes, otherwise it's the inner width of an element in pixels. It includes padding but not the vertical scrollbar (if present, if rendered), border or margin.
The Element.scrollTop property gets or sets the number of pixels that the content of an element is scrolled upward. An element's scrollTop is a measurement of the distance of an element's top to its topmost visible content. When an element content does not generate a vertical scrollbar, then its scrollTop value defaults to 0.
The Element.scrollWidth read–only property returns either the width in pixels of the content of an element or the width of the element itself, whichever is greater. If the element is wider than its content area (for example, if there are scroll bars for scrolling through the content), the scrollWidth is larger than the clientWidth.
The HTMLElement.offsetParent read-only property returns a reference to the object which is the closest (nearest in the containment hierarchy) positioned containing element. If the element is non-positioned, the nearest table cell or root element (html in standards compliant mode; body in quirks rendering mode) is the offsetParent. offsetParent returns null when the element has style.display set to "none". The offsetParent is useful because offsetTop and offsetLeft are relative to its padding edge.