you just need to add an id to the image tag:
<div class="fieldGroup"> <img src="WA_ValidationToolkit/WAVT_CaptchaSecurityImages.php?field=Contact_me_gr oup_Security_code&width=140&height=50& bgcolor=000000&transparent=false&noisefreq =25&gridfreq=50&gridcolor=FFFFFF&grido rder=0&font=Fonts/MODERNA_.TTF&textcolor=990000" alt="Security Code" class="Captcha" id="captchaImage" /> </div>
and add the script as:
<script language="JavaScript">
function reloadImage() {
var now = new Date();
if (document) {
document.getElementById('captchaImage').src = "WA_ValidationToolkit/WAVT_CaptchaSecurityImages.php?field=Contact_me_gr oup_Security_code&width=140&height=50& bgcolor=000000&transparent=false&noisefreq =25&gridfreq=50&gridcolor=FFFFFF&grido rder=0&font=Fonts/MODERNA_.TTF&textcolor=990000";
}
}
</script>