[BZ 1144052] - On group creation error, info messages are under fadeout window - the z-index css attribute was ignored, because there were two different so called stacking contexts. By setting the z-index to the default value (which is auto) to all related parent elements we prevent creating new stacking contexts. In other words z-index works correctly only for leave elements in the DOM tree, but if we combine different z-indices in one sub-tree it causes strange behavior.