Why is my HTML table not respecting my CSS column

Question

I have a HTML table and I want the first few columns to be quite long. I am doing this in CSS:

td.longColumn
{ 
     width: 300px;
}

and here is a simplified version of my table

<table>
  <tr>
   <td class='longColumn'></td>
   <td class='longColumn'></td>
   <td class='longColumn'></td>
   <td></td>
   <td></td>
   <td></td>
   <td></td>
   <td></td>
   [ . . and a bunch more columns . . .]
  </tr>
</table>

For some reason the table seems to make this column < 300px when there are a lot of columns. I basically want it to keep that width no matter what (and just increase the horizontal scroll bar).

The container that the table is inside, doesn't have any type of max width so I can't figure out why it's squeezing this column down as opposed to respecting this width.

Is there anyway around this so no matter what, this column will stay a certain width?
Here is the CSS of the outer container div:

#main
{
    margin: 22px 0 0 0;
    padding: 30px 30px 15px 30px;
    border: solid 1px #AAAAAA;
    background-color: #fff;
    margin-bottom: 30px;
    margin-left: 10px;
    _height: 1px; /* only IE6 applies CSS properties starting with an underscrore */
    float: left;
    /*width: 1020px;*/
    min-width:1020px;
    display: block;
    overflow: visible;
    z-index: 0;
}

Answer 1

The best way to set your column widths (td's) is to use a table header (th's). Table headers will set the width on your td's automatically. You just have to make sure that your columns inside your thead are the same number of columns in your tbody.

Check it out here: http://jsfiddle.net/tKAj8/

HTML

<table>
    <thead>
        <tr>
            <th class="short-column">Short Column</th> <!-- th sets the width -->
            <th class="short-column">Short Column</th> <!-- th sets the width -->
            <th class="long-column">Long Column</th> <!-- th sets the width -->
        </tr>
    </thead>

    <tbody>
        <tr>
            <td class="lite-gray">Short Column</td> <!-- td inherits th width -->
            <td class="lite-gray">Short Column</td> <!-- td inherits th width -->
            <td class="gray">Long Column</td> <!-- td inherits th width -->
        </tr>
    </tbody>
</table>

CSS

table { table-layout: fixed; border-collapse: collapse; border-spacing: 0; width: 100%; }

.short-column { background: yellow; width: 15%; }
.long-column { background: lime; width: 70%; }

.lite-gray { background: #f2f2f2; }
.gray { background: #cccccc; }

Answer 2

Use table-layout property and the "fixed" value on your table.

table {
    table-layout: fixed;
    width: 300px; /* your desired width */
}

After setting up the entire width of the table, you can now setup the width in % of the td's.

td:nth-child(1), td:nth-child(2) {
    width: 15%;
}

You can learn more about in on this link: http://www.w3schools.com/cssref/pr_tab_table-layout.asp

Answer 3

I had issues with not being able to size columns in a table-layout: fixed table that was using a colspan. For the benefit of anyone experiencing a variant of that issue where the suggestion above doesn't work, colgroup worked for me (variation on OP's code):

div {
    margin: 22px 0 0 0;
    padding: 30px 30px 15px 30px;
    border: solid 1px #AAAAAA;
    background-color: #fff;
    margin-bottom: 30px;
    margin-left: 10px;
    _height: 1px; /* only IE6 applies CSS properties starting with an underscrore */
    float: left;
    /*width: 1020px;*/
    min-width:1020px;
    display: block;
    overflow: visible;
    z-index: 0;
}
td.longColumn { 
     width: 300px;
}
table {
    border: 1px solid; 
    text-align: center;
    width: 100%;
}
td, tr {
  border: 1px solid; 
}

<div>
    <table>
        <colgroup>
            <col class='longColumn' />
            <col class='longColumn' />
            <col class='longColumn' />
            <col/>
            <col/>
            <col/>
            <col/>
        </colgroup>
        <tbody>
        <tr>
            <td colspan="7">Stuff</td>
        </tr>
        <tr>
            <td>Long Column</td>
            <td>Long Column</td>
            <td>Long Column</td>
            <td>Short</td>
            <td>Short</td>
            <td>Short</td>
            <td>Short</td>
        </tr>
        </tbody>
    </table>
</div>