function getCookie(c_name) {
    if (document.cookie.length>0) {
        c_start=document.cookie.indexOf(c_name + "=");
        if (c_start!=-1) {
            c_start=c_start + c_name.length+1;
            c_end=document.cookie.indexOf(";",c_start);
            if (c_end==-1) c_end=document.cookie.length;
            return unescape(document.cookie.substring(c_start,c_end));
        }
    }
    return "";
}

function checkCaptcha() {
    // check captcha
    var sInsCaptcha = calcMD5($('.captcha').val());
    var sCookieCaptcha = getCookie('strSec');

    if (sInsCaptcha == sCookieCaptcha) {
        alert('Wow, great, you enter correct captcha');
    } else {
        alert('Captcha errado');
    }
}