See the splitter documentation
This is the left side of the vertical splitter, which never has a scrollbar. If it did, it would have an ugly gap against the skinny splitbar.
The splitbar needs to be wide enough that it's easy to grab with the mouse. However, a thick splitbar may be visually distracting in a design. This example shows how to make a splitbar that looks skinny but has a wider grabbing area. It also demonstrates the use of an alternate resize cursor. (Not all browsers support alternate cursors and only IE seems to support animated cursors.)
A background image in the splitbar provides the visual marker but the splitbar area extends further left and right, appearing to be padding on the adjacent panes.
This technique is easiest to apply when both panes are the same background color and the left-hand pane doesn't need a scrollbar. However, by creating a custom background for the entire width of the splitbar, you can match differing background colors for the left and right panes.