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HTML Col, Colgroup Tutorial with Examples

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1- ColGroup, Col

<col> and <colgroup> tags represents for a column and a column group of a table.
<colgroup> is subtag of <table>. It is located after <caption>, and before <thead>, <tbody>, <tfoot>, <tr>. A table can have 0 or more <colgroup> subtags, and each <colgroup> has 0 or more <col> subtags. 
If <colgroup> has no <col> subtag:

<colgroup span = "<number>">
</colgroup>
It is equivalent to:

<colgroup>
     <col span = "<number>" />
</colgroup>
Example:
simple-colgroup-example.html

<!DOCTYPE html>
<html>
   <head>
      <title>Table align</title>
      <meta charset="UTF-8"/>
      <style>
         table, th, td {
         border: 1px solid black;
         }
         th, td {
         padding: 10px;
         }
      </style>
   </head>
   <body>
      <h2>HTML colgroup</h2>
      <table>
         <colgroup>
            <col  span ="3" style="background-color:lightblue">
         </colgroup>
         <tr>
            <th>No</th>
            <th>ISBN</th>
            <th>Title</th>
            <th>Price</th>
            <th>Description</th>
         </tr>
         <tr>
            <td>1</td>
            <td>3476896</td>
            <td>My first HTML</td>
            <td>$53</td>
            <td>..</td>
         </tr>
         <tr>
            <td>2</td>
            <td>5869207</td>
            <td>My first CSS</td>
            <td>$49</td>
            <td>..</td>
         </tr>
      </table>
   </body>
</html>
Example, a table has many <colgroup>:
colgroup-example.html

<!DOCTYPE html>
<html>
   <head>
      <title>HTML Colgroup, Col</title>
      <meta charset="UTF-8"/>
      <style>
         table, th, td {
         border: 1px solid black;
         }
         th, td {
         padding: 10px;
         }
      </style>
   </head>
   <body>
      <h2>HTML Colgroup, Col</h2>
      <table>
         <colgroup>
            <col style="background-color:lightgreen;width: 50px;"/>
         </colgroup>
         <colgroup style="background-color:yellow;">
            <col span="2"/>
            <col style="width: 90px;"/>
         </colgroup>
         <tr>
            <th>No</th>
            <th>ISBN</th>
            <th>Title</th>
            <th>Price</th>
            <th>Description</th>
         </tr>
         <tr>
            <td>1</td>
            <td>3476896</td>
            <td>My first HTML</td>
            <td>$53</td>
            <td>..</td>
         </tr>
         <tr>
            <td>2</td>
            <td>5869207</td>
            <td>My first CSS</td>
            <td>$49</td>
            <td>..</td>
         </tr>
      </table>
   </body>
</html>

2- Colgroup, Col Styles

Only a few CSS properties can​​​​​​​ apply to <colgroup>, <col>.
CSS border
CSS border will only work with a Collapsing Table. See the following example
CSS background-*
CSS background-* of <colgroup>, <col> only works in the places in which a table row or cell is transparent.
CSS width
Set up the width of <col>, <colgroup>.
CSS {visibility: collapse}
You can apply CSS visibility to <colgroup>, <col> but only to the {visibility:collapse} value. Other values are invalid and are ignored, or treated like {visibility:visible}.
CSS border
CSS border applying to <col>, <colgroup> works only with a Collapsing Table.
colgroup-border-example.html

<!DOCTYPE html>
<html>
   <head>
      <title>HTML Colgroup, Col</title>
      <meta charset="UTF-8"/>
      <style>
         table, th, td {
         border: 1px solid black;
         border-collapse: collapse;
         }
         th, td {
         padding: 10px;
         }
      </style>
   </head>
   <body>
      <h2>HTML Colgroup, Col</h2>
      <p style="color:blue; font-style:italic;">
         CSS border for COL, COLGROUP works only in Collasing Table.
      </p>
      <table>
         <colgroup>
            <col style="background-color:lightgreen;width: 50px;"/>
         </colgroup>
         <colgroup style="background-color:yellow; border: 3px solid red;">
            <col span="2"/>
            <col style="width: 90px;"/>
         </colgroup>
         <tr>
            <th>No</th>
            <th>ISBN</th>
            <th>Title</th>
            <th>Price</th>
            <th>Description</th>
         </tr>
         <tr>
            <td>1</td>
            <td>3476896</td>
            <td>My first HTML</td>
            <td>$53</td>
            <td>..</td>
         </tr>
         <tr>
            <td>2</td>
            <td>5869207</td>
            <td>My first CSS</td>
            <td>$49</td>
            <td>..</td>
         </tr>
      </table>
   </body>
</html>

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