function validateForm() {

 var error="";
 var d=document.forms[0];

 if(d.name.value.length<4) error+="*) Please indicate your name." +"\n";
 if(d.tel.value.length<7) error+="*) Please indicate a phone number." +"\n";
 if(!validEmail(d.mail.value)) error+="*) Please indicate a valid E-Mail-Address.";
 
 

  
 if(error!="") {
  alert("We need to have the following information.\n\nThank you!" +"\n\n" +error);
  return false;
 }
 else return true;
}

function validEmail(mail) {
  var strReg = "^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$";
  var regex = new RegExp(strReg);
  return(regex.test(mail));
}