code: private String getSingleSlotHtml(TestSlot s, String icon) {
      StringBuilder builder = new StringBuilder();
      TestSession session = s.getSession();
      if (icon != null) {
        builder.append("<img ");
        builder.append("src='").append(icon).append("' width='16' height='16'");
      } else {
        builder.append("<a href='#' ");
      }
  
      if (session != null) {
        builder.append(" class='busy' ");
        builder.append(" title='").append(session.get("lastCommand")).append("' ");
      } else {
        builder.append(" title='").append(s.getCapabilities()).append("'");
      }
  
      if (icon != null) {
        builder.append(" />\n");
      } else {
        builder.append(">");
        builder.append(s.getCapabilities().get(CapabilityType.BROWSER_NAME));
        builder.append("</a>");
      }
      return builder.toString();
    }
docs: icon ( or generic html if icon not available )