function ShowSpan(elementId) {
    var elem = document.getElementById(elementId);
    if (elem) {elem.style.display = ''; }
};

function HideSpan(elementId) {
    var elem = document.getElementById(elementId);
    if (elem) { elem.style.display = 'none'; }
};

function validateEmpty(elementId, errorText) {
    var element = document.getElementById(elementId);
    if (element!=null && element.value.length == 0) {
        alert(errorText);
        element.focus();
        return false;
    }
    return true;
}

function isValidEmail(rsEmail) {
    if ((rsEmail.indexOf("@") == -1) || (rsEmail.indexOf(".") == -1) || (rsEmail.indexOf("@") > rsEmail.lastIndexOf(".")))
        return false;
    else
        return true;
}

function validateEmail(elementId, errorText) {
    var element = document.getElementById(elementId);
    if (element != null && isValidEmail(element.value) == false) {
        alert(errorText);
        element.focus();
        return false;
    }
    return true;
}

function validateURL(elementId, errorText) {
    var element = document.getElementById(elementId);
    if (element != null && element.value != "" && isValidURL(element.value) == false) {
        alert(errorText);
        element.focus();
        return false;
    }
}

function isValidURL(url) {
    var regexp = /(ftp|http|https):\/\/(\w+:{0,1}\w*@)?(\S+)(:[0-9]+)?(\/|\/([\w#!:.?+=&%@!\-\/]))?/
    return regexp.test(url);
}