run the attached example (smooth-frozen-overlap.zul) and use the horzontal scrollbar
parts of the content overlap the frozen column
this happens for all 3 mesh widgets grid/listbox/tree
frozen columns should stay above the scrollable cells
the divs positioned relative/absolute overlap when scrolling to the left (and partially overlap for selected, hovered rows)
z-index on frozen cells has no effect without relative positioning
The z-index CSS property specifies the z-order of a positioned element and its descendants.
adding "position: relative" to the cells and a lower "z-index:0" for the non-frozen cells works in this scenario