More tags ...

<COLGROUP SPAN=3></COLGROUP>

defines a group of columns in the table and allows you to set properties of those columns.

<THEAD ...>, <TBODY ...> , <TFOOT ...>

<THEAD ...>, <TBODY ...>, and <TFOOT ...> establish groups of rows.

<THEAD ...> indicates that a group of rows are the header rows at the top of the table. <TBODY ...> indicates that a group of rows are body rows. <TFOOT ...> indicates that a group of rows are the footer rows at the bottom of the table.

 

For More : http://www.w3.org/TR/html4/struct/tables.html