This is the code from my main.template.php:

<div class="', ($var % 2 == 0 ? 'index_left':'index_right') ,'">
      <div class="content_box">
        <h2>', $category['title'] ,'</h2>';
		foreach ($main['files'][$category['id']] as $file) {
			echo '
        <div class="file file_index">
          <div class="icon">
            <a href="', $file['url'] ,'"><img src="', $file['image'] ,'" width="', $settings['image_width'] ,'" height="', $settings['image_height'] ,'" alt="', $file['title'] ,'" /></a>
          </div>
          <div class="desc">
            <p class="link"><a href="', $file['url'] ,'">', $file['title'] ,'</a></p>';
			if ($settings['stars_index'] == 1) {
				echo '
            <p><img src="', $settings['siteurl'] ,'/images/stars', $file['stars'] ,'.gif" width="67" height="15" title="', $file['rating'] ,'" alt="', $file['rating'] ,'" /></p>';
			} // if
			echo '
            <p>', $file['description'] ,'</p>
            <p class="played">(', $lang['played_times'] ,': ', $file['played'] ,')</p>
          </div>
        </div>';
		} // foreach
		echo '
        <div class="txt_right">
          <a href="', $category['url'] ,'">', $lang['more_in_category'] ,' ', $category['title'] ,' &gt;</a>
        </div>
      </div>
    </div>';
		if ($var % 2 == 1) {
			echo '
    <div class="clear"></div>';
		} // if
	} // foreach
	echo '
  </div>';

} // end function

This is the code from the CSS file:

/* index page 2 columns */
.index_left {
	float: left;
	width: 407px;
}
.index_right {
	float: right;
	width: 407px;
}

Now the page has 2 columns, and I want it with 3 columns. How can I do that? Any help is welcome.

i'm just gonna describe the whole idea of having 3 columns in a page.
first of all we need two div tags. then we give them the float attribute.
like this:

<div class="left-col" style="float:left;width:20%;">this is the contents of our left most column.</div>

<div class="right-wrapper" style="float:right;width:80%;"> ... </div>

so far we've got only 2 columns. for having the 3rd one we're gonna need 2 other DIVs placed inside the "right-wrapper".
we just do it like this:

<div class="left-col" style="float:left;width:20%;">this is the contents of our leftmost column.</div>

<div class="right-wrapper" style="float:right;width:80%;">
<div class="middle-col" style="float:left;width:60%;">this is the middle column.</div>
<div class="right-col" style="float:right;width:20%;">and this is the right and 3rd column.</div>
</div>

just like that we've got all 3 columns we needed.

Thank you for your help, but this is not what I want. I want to modify this code on 3 columns. If you see it's a single DIV with 2 classes (which are the two columns), made in CSS. This DIV is changing, because it's made for game categories on my main page. The categories are divided in two columns. But I would like 3.

sorry. I can't help you about that if I don't see the result of this code. if you could give a link to a page which you made using this code that's whole different matter.

ok... here is your modified code:

';
	if($var%3==1) echo '<div class="right_container">';
    echo '<div class="';
	switch($var%3){
		case 0:
		echo 'index_left';
		break;
		case 1:
		echo 'index_mid';
		break;
		case 2:
		echo 'index_right';
		break;
	}
    echo '">
      <div class="content_box">
        <h2>', $category['title'] ,'</h2>';
		foreach ($main['files'][$category['id']] as $file) {
			echo '
        <div class="file file_index">
          <div class="icon">
            <a href="', $file['url'] ,'"><img src="', $file['image'] ,'" width="', $settings['image_width'] ,'" height="', $settings['image_height'] ,'" alt="', $file['title'] ,'" /></a>
          </div>
          <div class="desc">
            <p class="link"><a href="', $file['url'] ,'">', $file['title'] ,'</a></p>';
			if ($settings['stars_index'] == 1) {
				echo '
            <p><img src="', $settings['siteurl'] ,'/images/stars', $file['stars'] ,'.gif" width="67" height="15" title="', $file['rating'] ,'" alt="', $file['rating'] ,'" /></p>';
			} // if
			echo '
            <p>', $file['description'] ,'</p>
            <p class="played">(', $lang['played_times'] ,': ', $file['played'] ,')</p>
          </div>
        </div>';
		} // foreach
		echo '
        <div class="txt_right">
          <a href="', $category['url'] ,'">', $lang['more_in_category'] ,' ', $category['title'] ,' &gt;</a>
        </div>
      </div>
    </div>';
    
		if ($var % 3 == 2) {
			echo '</div>';
			echo '
    <div class="clear"></div>';
		} // if
	} // foreach
	echo '
  </div>';

} // end function

and the css code would be like this:

/* index page 2 columns */
.right_container{
float:right;
}
      .index_left {

      float: left;

      width: 275px;
      overflow:scroll;

      }

      .index_right {

      float: right;

      width: 275px;

      overflow:scroll;

      }
.index_mid{
float:left;
width:275px;
overflow:scroll;
}

I attached a screen shot of what I got. you can tweak the style to make it the way you want.

commented: awsome :D +1

It's perfect :D Just what I was dreaming about. Thank you very very very much :D