function validate_email(field,alerttxt)
{
with (field)
{
apos=value.indexOf("@")
dotpos=value.lastIndexOf(".")
if (apos<1||dotpos-apos<2) 
  {alert(alerttxt);return false}
else {return true}
}
}
function validate_form(thisform)
{
with (thisform)
{
if (validate_email(txt_nieuws,"U gaf geen geldig e-mail adres op!")==false)
  {txt_nieuws.focus();return false}
}
}