var nbimage = 4 ;
var code;
var code2;

function Images_Aleatoire(){
myform=document.getElementById("form1");
code2=document.getElementById("code2field");
myform.code2.value="";

var numimage = Math.round( Math.random() * ( nbimage - 1 ) + 1 );
form1.img002.src="images/captcha"+numimage+".gif";

if (numimage==1){code="i5j8a";}
else if (numimage==2){code="pr67b";}
else if (numimage==3){code="46f7x";}
else if (numimage==4){code="k4y8m";}
}

function valid_code(){
myform=document.getElementById("form1");
if (myform.code2.value==code) {myform.send.disabled=false;}
else {myform.send.disabled=true;alert('The code you entered does NOT match');Images_Aleatoire();}
}