function isEmail(emailstr) {
    valid = /([a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+\.[a-zA-Z0-9._-]+)/gi;
    result = emailstr.match(valid);
    if (result == null) { return false; }
    return true;
 }
    
 function validateForm(theForm) {
    var msg = "";
    if (theForm.elements["name"].value == "") { msg += "\nName"; }
    if (theForm.elements["telephone"].value == "") { msg += "\nTelephone number"; }
    if (!isEmail(theForm.elements["email"].value)) { msg += "\nE-mail address"; }

    if (msg != "") {
        alert("Please complete the following compulsory fields correctly:" + msg);
        return false;
    }
    return true;
 }
 
 function validateSimpleForm(theForm) {
    var msg = "";
    if (theForm.elements["name"].value == "") { msg += "\nName"; }
    if (!isEmail(theForm.elements["email"].value)) { msg += "\nE-mail address"; }

    if (msg != "") {
        alert("Please complete the following compulsory fields correctly:" + msg);
        return false;
    }
    return true;
 } 
 
 function checkForHiddenFormFields(selectBox) {

    // this js specific to marketingnet contact form
    var secretFields = 3;
    // hide all secret fields
    for (i=1; i<=secretFields; i++) {
        fieldToHide = selectBox.name + "_extra_" + i;
        elementToHide = document.getElementById(fieldToHide);
        hideHiddenFormField(elementToHide);
    }
    // if the selected option matches one of the hidden field options display correct one
    selectedIndex = selectBox.selectedIndex;
    indexID = selectBox[selectedIndex].id;
    if ((indexID != null) && (indexID != "")) {
        fieldToShow = selectBox.name + indexID;
        if (document.getElementById(fieldToShow)) {
            elementToShow = document.getElementById(fieldToShow);
            showHiddenFormField(elementToShow);
        }
    }
 }
 
 function showHiddenFormField(element) {
    element.style.display = "block";
 }
 
 function hideHiddenFormField(element) {
     element.style.display = "none";
 }