var regex = new RegExp("[a-z0-9._-]{1,}@[a-z0-9.-]{3,}", "gi");

var message0 = "- Please fill in your name.\n";
var message1 = "- Please fill in your e-mail address.\n";
var message2 = "- You can only register after agreeing to the business terms of ISK.\n";
var message3 = "- Yhave received the information of the power to revocation of the distance selling contract.\n";

function controles()
{        var message = "";
         if (document.form1.Name.value.length == 0)
                { message += message0;}
         if (document.form1.Email.value.search(regex) == -1)
                { message += message1;}
         if (document.form1.Bedingungen.checked == false)
                { message += message2; }
 if (document.form1.Widerrufsrecht.checked == false)
                { message += message3; }
if (message.length > 0)
     { window.alert("Your message has not been sent. \n\n" + message);}
  else
     { document.form1.submit();}
}