function emailcheck(){
var email=document.EmailKontaktOs.Email.value;
if (email==""){
alert("You have to enter an E-mail")
document.EmailKontaktOs.Email.focus()
return false
}
if (email!=""){
        if (email.indexOf('@', 0) == -1 || email.indexOf('.', 0) == -1){ 
        alert("You havne not entered a correct e-mail. Try again!");
document.EmailKontaktOs.Email.focus()
return false
}
}
}