function tha(numb)
{	
	var i,
	li=document.getElementById("nav").getElementsByTagName("a");	
	for(i=0;i<li.length;i++)
	{		
		if(i==numb)
		{	
		   // alert(i);
			document.getElementById("submenu"+i).style.display ="";
			li[i].className="menu"+(i+1)+"_on";
		}
		else
		{
			document.getElementById("submenu"+i).style.display ="none";;
			li[i].className="menu"+(i+1);
		}
	}
}