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