var current = 1;

var oInterval = "";

function fnStartInterval(){
   oInterval = window.setInterval("Swap()",2000);
}
function Swap(){     
   var ran_unrounded=Math.random()*4;
	var ran_number=Math.round(ran_unrounded); 
	
	
 	var o1 = document.getElementById("main_1");      
   var o2 = document.getElementById("main_2");      
   var o3 = document.getElementById("main_3");      

   if(ran_number == 1)
   {
	   ShowMain(o1);
	   HideMain(o2);
	   HideMain(o3);
	   //current ++;
	}
	else if(ran_number == 2)
	{	
		HideMain(o1);
	   ShowMain(o2);
	   HideMain(o3);
	   //current ++;
	}
	else if(ran_number == 3)
	{
		HideMain(o1);
	   HideMain(o2);
	   ShowMain(o3);
	   //current = 1;
	} 
	else
	{
		HideMain(o1);
	   HideMain(o2);
	   ShowMain(o3);
	}
}
function HideMain(e)
{
	e.style.display = "none";
}
function ShowMain(e)
{
	e.style.display = "block";
	
}