border-collapse: separate
head 1 head 2 head 3 head 4
cell 1 cell 2 cell 3
cell 4 cell 5
cell 6
cell 7
border-collapse: collapse
head 1 head 2 head 3 head 4
cell 1 cell 2 cell 3 cell 4
cell 5 cell 6 cell 7
cell 8 cell 9 cell 10
cell 11