Description:

The <colgroup> tag is used to group columns in a table for formatting.

The <colgroup> tag is useful for applying styles to entire columns, instead of repeating the styles for each cell, for each row.

The <colgroup> tag can only be used inside a table element.

Example Code:
<table width="100%" border="1">
  <colgroup span="2" align="left"></colgroup>
  <colgroup align="right" style="color:#0000FF;"></colgroup>
  <tr>
    <th>ISBN</th>
    <th>Title</th>
    <th>Price</th>
  </tr>
  <tr>
    <td>3476896</td>
    <td>My first HTML</td>
    <td>$53</td>
  </tr>
</table>
Result:
ISBN Title Price
3476896 My first HTML $53
Attributes:
Attribute Definition
span Specifies how many columns to span.
width Width of the column.
align Specifies the alignment of the content related to a col element.
valign Specifies the vertical alignment of the content related to a col element.
char Specifies the alignment of the content related to a col element to a character.
charoff Specifies the number of characters the content will be aligned from the character specified by the char attribute.
Global Attributes:

The <colgroup> tag also supports the Global Attributes in HTML5

Event Attributes:

The <colgroup> tag also supports the Event Attributes in HTML5