// set active tabs
function setNavClass(navID){
	$('.on').removeClass('on');
	$('#'+navID).addClass('on');
}

// initialise the move
function startMove(pos, NavClass){	
	$('.slide').animate({ left: -pos }, 500);
}

// change the navigation (perform all functions)
function changeNav(nav){
	if (nav == 1){
		if (document.getElementById('headerimage') != null){
			startMove(0, 'slide_1');
			setNavClass('slide_1');
		}
		return false;
	}
	if (nav == 2){
		if (document.getElementById('headerimage') != null)
		{	
			startMove(940, 'slide_2');
			setNavClass('slide_2');
		}					
		return false;
	}
	if (nav == 3){
		if (document.getElementById('headerimage') != null){
			startMove(1880, 'slide_3');
			setNavClass('slide_3');
		}
		return false;
	}
	if (nav == 4){
		if (document.getElementById('headerimage') != null){
			startMove(2820, 'slide_4');
			setNavClass('slide_4');
		}
		return false;
	}
	if (nav == 5){
		if (document.getElementById('headerimage') != null){
			startMove(3760, 'slide_5');
			setNavClass('slide_5');
		}
		return false;
	}
}