Cannot put margin on tag with neither CSS nor cellspacing attribute

If someone still has this problem, try this in your CSS stylesheet:

table {
  border-collapse: separate;
  border-spacing: 10px 5px;
}

The values for border-spacing are two length measurements. The horizontal
value comes first and applies between columns. The second measurement is
applied between rows.

If you provide one value, it will be used both horizontally and vertically. The default setting is 0, causing the borders to double up on the inside grid of the table.