Table with table-layout: fixed; and how to make one column wider

You could just give the first cell (therefore column) a width and have the rest default to auto

table {
  table-layout: fixed;
  border-collapse: collapse;
  width: 100%;
}
td {
  border: 1px solid #000;
  width: 150px;
}
td+td {
  width: auto;
}

<table>
  <tr>
    <td>150px</td>
    <td>equal</td>
    <td>equal</td>
  </tr>
</table>

or alternatively the "proper way" to get column widths might be to use the col element itself

table {
  table-layout: fixed;
  border-collapse: collapse;
  width: 100%;
}
td {
  border: 1px solid #000;
}
.wide {
  width: 150px;
}

<table>
  <col span="1" class="wide">
    <tr>
      <td>150px</td>
      <td>equal</td>
      <td>equal</td>
    </tr>
</table>

The important thing of table-layout: fixed is that the column widths are determined by the first row of the table.

So

if your table structure is as follow (standard table structure)

<table>
  <thead>
      <tr>
          <th> First column </th>
          <th> Second column </th>
          <th> Third column </th>        
      </tr>
  </thead>

   <tbody>
      <tr>
          <td> First column </td>
          <td> Second column </td>
          <td> Third column </td>        
      </tr>
  </tbody>

if you would like to give a width to second column then

<style> 
    table{
        table-layout:fixed;
        width: 100%;
    }

    table tr th:nth-child(2){
       width: 60%;
     }

</style>

Please look that we style the th not the td.

Are you creating a very large table (hundreds of rows and columns)? If so, table-layout: fixed; is a good idea, as the browser only needs to read the first row in order to compute and render the entire table, so it loads faster.

But if not, I would suggest dumping table-layout: fixed; and changing your css as follows:

table th, table td{
border: 1px solid #000;
width:20px;  //or something similar   
}

table td.wideRow, table th.wideRow{
width: 300px;
}

http://jsfiddle.net/6p9K3/1/

What you could do is something like this (pseudocode):

<container table>
  <tr>
    <td>
      <"300px" table>
    <td>
      <fixed layout table>

Basically, split up the table into two tables and have it contained by another table.