function killNaNs(field){
    var c = field.value;
    if(isNaN(c)){
        field.value = "";
    }
}

var addToCartURL = "";
function setAddToCartURL(url){
    addToCartURL = url;
}
var cartDisplayURL = "";
function setCartDisplayURL(url){
    cartDisplayURL = url;
}
function displayCheckout(){
    document.getElementById('checkout').style.display = 'block';
}

function addItemToCart(form){
    displayCheckout();
    if(addToCartURL != ""){
        var c = form.elements.length;
        param = "?";
        for(var i = 0; i<c; i++){
            var val = form.elements[i].value;
            param += form.elements[i].name +"="+escape(val)+"&";
        }
        param +='cartDisplay='+cartDisplayURL;
        parent.frames['cartframe'].location.href=addToCartURL+param;
    }
    return false;
}