function checkform() 
    {
        var mail = document.contact.mail.value;
        var name = document.contact.name.value;
        var message = document.contact.message.value;
        
        if(mail == '' || name == '' || message == '')
        {
            document.getElementById("alert_content").innerHTML = "<img src='/_lib/img/alert.png'> &nbsp;" + document.getElementById("alert_error").innerHTML;
           
            return false;
        }
        if (!emailCheck(mail))
        {
            document.getElementById("alert_content").innerHTML = "<img src='/_lib/img/alert.png'> &nbsp;" + document.getElementById("alert_error_mail").innerHTML;
           
            return false;
        }
    
        return true;
    }
    
    function emailCheck(email){
        return /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/.test(email);
    }