function error(){
 var msg="";
 if(document.forms[0].name.value==""){msg+="Please enter a name.\n";}
 if(document.forms[0].mail.value==""){
  msg+="Please enter an e-mail.\n";
 }else{
  var reg=/^[a-zA-Z0-9._%-]+@[a-zA-z0-9.-]+\.[a-zA-Z]{2,4}$/;
  var answer=reg.test(document.forms[0].mail.value);
  if(!answer){msg+="Please enter a valid e-mail.\n";}}
 if(document.forms[0].text.value==""){msg+="You must enter a message.\n";}
 if(document.forms[0].cap.value==""){msg+="Please enter the text in the image.\n";}
 if(msg!=""){
  alert(msg);
  return false;}}