Check out example codes for "how to make a html captcha". It will help you in understanding the concepts better.

Code Example 1

COPY THIS AND THEN USE IT ON YOUR WEBPAGE
<!DOCTYPE html>
<html>
<body>

<form id="DemoForm" action="https://www.SnapHost.com/captcha/send.aspx" method="post" target="_top">
<input id="skip_SnapHostID" name="skip_SnapHostID" type="hidden" value="DEMO12345678">
<input id="skip_WhereToSend" name="skip_WhereToSend" type="hidden" value="support[[]]snaphost.com">
<input id="skip_WhereToReturn" name="skip_WhereToReturn" type="hidden" value="https://www.snaphost.com/captcha/ThankYou.aspx?isSent=success">
<input id="skip_Subject" name="skip_Subject" type="hidden" value="Subject test">

<table border="0" cellpadding="5" cellspacing="0">
<tbody><tr>
    <td colspan="2" align="center">  </td>
</tr>






</tbody></table>
<br>

<table cellspacing="0" border="0" cellpadding="8">
<tbody><tr>
    
</tr>
<tr style="background-color:#ffcc66; vertical-align:bottom;">
    <td>
        <input id="skip_CaptchaCode" name="skip_CaptchaCode" type="text" style="width:130px;height:48px;font-size:38px;" maxlength="6"><br>
        <i>Enter web form code</i>
    </td>
    <td>
        <a href="#" onclick="return ReloadCaptchaImage('CaptchaImage');"><span style="font-size:12px;">reload image</span></a><br>
        <a href="https://www.SnapHost.com/captcha/ProCaptchaOverview.aspx"><img id="CaptchaImage" alt="Web Form Code" style="border-width:0px;" src="https://www.SnapHost.com/captcha/CaptchaImage.aspx?id=DEMO12345678"></a>
        <script type="text/javascript" async="" src="https://ssl.google-analytics.com/ga.js"></script><script type="text/javascript">
            function ReloadCaptchaImage(captchaImageId) {
                var obj = document.getElementById(captchaImageId);
                var src = '' + obj.src;
                obj.src = '';
                var date = new Date();
                var pos = src.indexOf('&rad=');
                if (pos >= 0) { src = src.substr(0, pos); }
                obj.src = src + '&rad=' + date.getTime();
                return false;
            }
        </script>
    </td>
</tr>
</tbody></table>

<br><br>

<input id="skip_DemoSubmit" name="skip_DemoSubmit" type="submit" value="Submit">
    
<br>

</form>
</body>
</html>

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