function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value=="")
  {alert(alerttxt);return false;}
else {return true}
}
}

function validate_form(thisform)
{
with (thisform)
{
if (validate_required(your_name,"We must have your name to contact you.")==false)
  {your_name.focus();return false;}
if (validate_required(your_email,"We must have your email to contact you.")==false)
  {your_email.focus();return false;}
if (validate_required(your_telephone,"We must have your telephone number to contact you.")==false)
  {your_telephone.focus();return false;}
}
}