var selectedIndex = "0";
var numberOfTabs  = 3;

function showView(obj){
    if(selectedIndex == obj.id)
        return;
    
    document.getElementById(selectedIndex).className = "product-display-navitem";

    selectedIndex = obj.id;    
    obj.className = "product-display-navitem navitem-selected";
    	
    var offset = parseInt(obj.id) * 930 * -1;
	var offsetCSS = offset.toString() + "px";

    document.getElementById("product-display-content").style.left = offsetCSS;
}

function showNext(){
    var selectedIndexNumber = parseInt(selectedIndex);
    selectedIndexNumber++;
    
    if(selectedIndexNumber > numberOfTabs)
        selectedIndexNumber = 0;
        
    var obj = document.getElementById(selectedIndexNumber.toString());
    showView(obj);    
}

function showPrev(){
    var selectedIndexNumber = parseInt(selectedIndex);
    selectedIndexNumber--;
    
    if(selectedIndexNumber < 0)
        selectedIndexNumber = numberOfTabs;
        
    var obj = document.getElementById(selectedIndexNumber.toString());
    showView(obj);
}