colgroup

If the colgroup element contains no col elements, then the element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

<html>
<body>
<table border="1" border="2" rules="groups">
 <!-- RULES is set to "groups" which places internal dividing lines around 
table border="1" columns defined by COLGROUP. -->
 <colgroup span="2" style="color: red">
 </colgroup>
 <colgroup style="color: blue">
 </colgroup>
 <tr>
 <td>This column is in the first group.</td>
 <td>This column is in the first group.</td>
 <td>This column is in the second group.</td>
 </tr>
 <tr>
 <td>This column is in the first group.</td>
 <td>This column is in the first group.</td>
 <td>This column is in the second group.</td>
 </tr>
</table border="1">
</body>
</html>
This column is in the first group.This column is in the first group.This column is in the second group.
This column is in the first group.This column is in the first group.This column is in the second group.
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