function themeoptions_update()
{
    // this is where validation would go
    update_option('mytheme_colour',     $_POST['colour']);

    update_option('mytheme_ad1image',   $_POST['ad1image']);
    update_option('mytheme_ad1url',     $_POST['ad1url']);

    update_option('mytheme_ad2image',   $_POST['ad2image']);
    update_option('mytheme_ad2url',     $_POST['ad2url']);

    if ($_POST['display_sidebar']=='on') { $display = 'checked'; } else { $display = ''; }
    update_option('mytheme_display_sidebar',    $display);

    if ($_POST['display_search']=='on') { $display = 'checked'; } else { $display = ''; }
    update_option('mytheme_display_search',     $display);

    if ($_POST['display_twitter']=='on') { $display = 'checked'; } else { $display = ''; }
    update_option('mytheme_display_twitter',    $display);

    update_option('mytheme_twitter_username',   $_POST['twitter_username']);
}