function submitting()
{
   var s="";
   if (document.mainform.FirstName.value=="") s+="\n- FirstName";
   if (document.mainform.LastName.value=="") s+="\n- LastName";
   if (document.mainform.Email.value=="") s+="\n- Email";
   if (document.mainform.terms.checked  == false) s+="\n- terms and conditions";
   if (s!="")
   {
     alert("Please enter the following fields:"+s);
     return false;
   }

   if (-1 == document.mainform.Email.value.indexOf("@") || -1 == document.mainform.Email.value.indexOf("."))

   {
     alert("Please enter a valid Email address");
     return false;
   }
   return true;
}