function Captcha(){
var alpha = new Array('A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
'0','1','2','3','4','5','6','7','8','9');
var i;
for (i=0;i<20;i++){
var a = alpha[Math.floor(Math.random() * alpha.length)];
var b = alpha[Math.floor(Math.random() * alpha.length)];
var c = alpha[Math.floor(Math.random() * alpha.length)];
var d = alpha[Math.floor(Math.random() * alpha.length)];
var e = alpha[Math.floor(Math.random() * alpha.length)];
var f = alpha[Math.floor(Math.random() * alpha.length)];
var g = alpha[Math.floor(Math.random() * alpha.length)];
var h = alpha[Math.floor(Math.random() * alpha.length)];
var i = alpha[Math.floor(Math.random() * alpha.length)];
var j = alpha[Math.floor(Math.random() * alpha.length)];
}
var code = a + ' ' + b + ' ' + ' ' + c + ' ' + d + ' ' + e + ' '+ f + ' ' + g + ' ' + h + ' ' + i + ' ' + j;
document.getElementById("mainCaptcha").innerHTML = code
document.getElementById("mainCaptcha").value = code
}