The HTML code for the tables will be displayed at the end of the page. Header cells are identical to data cells, but the text in them is shown in bold type, and the data is centered. You can control the horizontal and vertical alignment of the contents of your table. The table below contains examples. Left is the default.
Possible values are top, middle, or bottom.
Middle is the default. It defines the amount of space between the individual cells in a table. This is just a start. Yet Another Document on advanced tables available close by. Take a look.