function checkContact(form) {

if (form.naam.value == "") {
        alert( "Please fill in your name" );
        form.naam.focus();
        return false ;
    }

//Een correcte email check
var emailAdres = form.email.value;
valid = new RegExp("^[a-zA-Z0-9]+([.]?[a-zA-Z0-9_-]+)*[@]([a-zA-Z0-9_-]+[.])+([a-zA-Z]{2,4})$").exec(emailAdres);
if(!valid) { 
   alert( "Please fill in a valid e-mail adres" );
   form.email.focus();
   return false;
   }
if (form.bericht.value == "") {
        alert( "Please fill in a message" );
        form.bericht.focus();
        return false ;
    }

 return true;
}