Defines whether table borders should be separated or collapsed.
默认属性
border-collapse: separate;
Each table cell will display its own borders.
In this example, each cell has a border-width of 4px. As a result, the border between two cells will be 8px.
border-collapse: collapse;
Adjacent table cells will merge their borders together.
The cell that appears first in the code will "win": its borders will mask those of the following cells.