function validateEmail() {
 
    foundError = false;
 
    if(isBlank(document.emailform.yourname)){
        alert("Please enter your name!");
        foundError = true;
    }
    if(foundError == false && isBlank(document.emailform.emailaddress) && isBlank(document.emailform.telephone)){
        alert("Please enter either your email address or your telephone number!");
        foundError = true;
    }
    if (foundError == false){
        document.emailform.submit();
    }
}
 
function isBlank(theField){
    if(theField.value == "")
        return true;
    else
        return false;
}