function swap_selected(elem){
   if(elem){
      //return if you clicked the selected tab
      if(elem.className == "selected") return; 

      var tab_1 = document.getElementById("T1");
      var tab_2 = document.getElementById("T2");
      var tab_3 = document.getElementById("T3");
      
      var content_1 = document.getElementById("C1");
      var content_2 = document.getElementById("C2");
      var content_3 = document.getElementById("C3");
      			
      if(elem == tab_1){
         tab_1.className = "selected";
         content_1.style.display = "inline";

         tab_2.className = "";
         content_2.style.display = "none";
				 tab_3.className = "";
         content_3.style.display = "none";

               }
			
      else if(elem == tab_2){
         tab_2.className = "selected";
         content_2.style.display = "inline";

         tab_1.className = "";
         content_1.style.display = "none";
         
         tab_3.className = "";
         content_3.style.display = "none";

              }
     	 else if(elem == tab_3){
         tab_3.className = "selected";
         content_3.style.display = "inline";

         tab_2.className = "";
         content_2.style.display = "none";

         tab_1.className = "";
         content_1.style.display = "none";

       				 
      }
      
			   }
}