SemanSemantic-UItic-UI/docs/ui/flat/modules/tab.css

/*******************************
           UI Tabs 
*******************************/

.ui.tab {
  display: none;
  background-color: #FFFFFF;
  border: 1px solid #DADADA;
  border-top-color: transparent;
  border-top-width: 0px;
}
.ui.tab.active,
.ui.tab.open {
  display: block;
}

.ui.tab.loading > .throbber {
	display: block;
}

.ui.tab.simple {
	background-color: transparent;
	border: none;
}