var form_error_mark_border  = "1px solid #000000";
var form_error_reset_border = "1px solid #777777";

function form_error_mark(field)
{
  field.style.border = form_error_mark_border;
  field.focus();
}

function form_error_reset(field)
{
  field.style.border = form_error_reset_border; 
}

function check_email(email)
{
  /* valid chars for email */
  var emailchars="@abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZaöüAÖÜ+-_.0123456789~";
  var emailchars_res = true;
  for(i=0; i<email.length; i++) 
  { 
    emailchars_res && (emailchars.indexOf(email.charAt(i))!=-1) 
  }
  
  /* check length, @, .@, !.xxxxx  */
  email_res = ( emailchars_res &&
                email.length >= 6 &&
                email.search('@') >= 1 &&
                email.lastIndexOf('.') > email.search('@') &&
                email.lastIndexOf('.') >= email.length-5
          	   )
  return email_res;
}