/**
 * Validate contact form
 */ 
function validateContactForm(fields) {
    
    var validated = true;
    var message = 'Please, fill in following fields:\n';

    for (var i = 0; i < fields.length; i++) {
        var field = document.getElementById(fields[i][0]);
        if (field.value == '') {
            message += fields[i][1] + '\n';
            validated = false;
        }
    }
    
    if (validated) {
        document.getElementById('contact-form').submit();
    } else {
        alert(message);
    }
}