+ Certain formatting contexts may establish what is known as a grouping box. + Other boxes can then be assigned to one or more of those [=grouping boxes=], which will encompass the entirety of the assigned box. + If a box is assigned to any [=grouping boxes=] and gets broken, + then for the purpose of filling any [=remaining fragmentainer extent=] as described above, + the [=remaining fragmentainer extent=] should be treated as if the [=fragmentainer=] it belongs to did not extend past the [=block-end=] of the [=grouping box=] that the break falls within. + +
+ Furthermore, if a box is assigned to any [=grouping boxes=] and the ancestors of those [=grouping boxes=] are broken between any two of the [=grouping boxes=], user agents should try to avoid creating box fragments for the [=assigned to|assigned box=], which span across that break. + +
+ One way of accomplishing this is to make sure that within any [=assigned to|assigned box=] there is at least one break, preceding each point where there is a break between the [=grouping boxes=] that it is [=assigned to=]. + Care should be taken to ensure that there is enough space below said break in the [=grouping box=] to fit any cloned margins/border/padding so that they do not cause the [=assigned to|assigned box=] to extend beyond the [=grouping box=]. + +
+ Grouping boxes are established in the following situations: +