[Lynne]

You would do that for every td tag that you wish to change. I've seen some users only want to change the post background and that would be here in red:

    <if condition="$show['moderated']">
    <td class="alt2" id="td_post_$post[postid]">
    <else />
    <td class="alt1" id="td_post_$post[postid]">
    </if>

Make sure when you change it that all your <if> tags have a closing </if> tag.

x and y would be the usergroups.

To add another alt class, you would put it in the Main CSS for the style - at the bottom of that page.