Auto fill hidden fields

Add to CSS

/* hide referral field in form #2 */
#form_submission_custom_2 {display:none;}

#form_submission_name {display:none;}

#form_submission_email {display:none;}

Add to Script

var Params = window.location.search.substr(1).split('&');
for(var i = 0; i < Params.length; i++){
var p = Params[i].split('=');
if (p[0] == 'name') {
document.getElementById('form_submission_name').value = decodeURIComponent(p[1]);
}
if (p[0] == 'email') {
document.getElementById('form_submission_email').value = decodeURIComponent(p[1]);
}
if (p[0] == 'tagxyz') {
document.getElementById('form_submission_custom_2').value = decodeURIComponent(p[1]);
} 
}