function is_valid_email(str) {
   if(str=='') return false; 
   return (str.indexOf(".") > 2) && (str.indexOf("@") > 0);
}
function validate_form(){
    var name = document.getElementById('contact_name').value;
    var email = document.getElementById('contact_email').value;
    var type = document.getElementById('contact_type').value;
    var message = document.getElementById('contact_message').value;
    var err = new Array();
    
    if(!name) err.push('Name');
    if(!is_valid_email(email)) err.push('Email address');
    if(!type) err.push('Message type');
    if(!message) err.push('Message');
    
    if(err.length){
        alert('Please fill in the following fields:\n - '+err.join("\n - "));
        return false;
    }
    return true;
}