[Seven Skins]

You can try this:

.ss_twincolumns_wrapper {
  padding-left: 175px;
  padding-right: 175px;
}

.ss_twincolumns_inner {
  width: 100%;
}

.ss_twincolumns_floatwrap {
  float: left;
  width: 100%;
  margin-left: -175px;
}

.ss_twincolumns_content {
  float: right;
  margin-right: -175px;
  width: 100%;
  position: relative;
}

.ss_twincolumns_content_margin {
  padding: 0px 5px 0px 5px;
}

.ss_twincolumns_left {
  float: left;
  width: 175px;
  position: relative;
}

.ss_twincolumns_left_margin {
  padding: 10px 5px 0px 0px;
}

.ss_twincolumns_right {
  float: right;
  width: 175px;
  position: relative;
  margin-right: -175px;
  position: relative;
}

.ss_twincolumns_right_margin {
  padding: 10px 0px 0px 5px;
}

.ss_twincolumns_clear {
  clear: both;
}

.ss_column_head {
  background: {vb:stylevar forumhead_background};
  padding: 0;
  font:{vb:stylevar forumhead_font};
  color:{vb:stylevar forumhead_color};
  border: {vb:stylevar forumhead_border};
  -moz-border-radius-top{vb:stylevar right}: {vb:stylevar forumhead_top_corner_radius};
  -moz-border-radius-top{vb:stylevar left}: {vb:stylevar forumhead_top_corner_radius};
  -webkit-border-top-{vb:stylevar right}-radius: {vb:stylevar forumhead_top_corner_radius};
  -webkit-border-top-{vb:stylevar left}-radius: {vb:stylevar forumhead_top_corner_radius};
  padding: {vb:math {vb:stylevar padding}/2-1} 0;
}

.ss_column_body {
  background: {vb:stylevar forumrow_background};
  padding: 0;
  border-bottom: {vb:stylevar forumbits_border};
  border-{vb:stylevar left}: {vb:stylevar forumbits_border};
  border-{vb:stylevar right}: {vb:stylevar forumbits_border};
  margin-bottom: 8px;
}

PS. Code is not tested as I do not have this installed on any of my site.