I need the Opt-In Checkbox to be check by default

SOLUTION:

1. Click on top right Name or Account name in Web Forms interface

2. Select Custom Javascript

3. Paste the following custom JavaScript in the correct places

*note that this will make the opt-in checkbox selected by default across all lightboxes in the account

===========================

In Before Lightbox Display:

//Auto-check opt-in checkbox
var iframe = document.getElementById(“lightbox - iframe - ” +lbid);
if (iframe !== null) {
  var iframeDocument = iframe.contentDocument || iframe.contentWindow.document;
  if (iframeDocument) {
    var iframeOptIn = iframeDocument.getElementById(‘form_input_opt_in’);
    if (iframeOptIn) {
      iframeOptIn.checked = PRIMER_CUSTOM_JS_GLOBAL.precheck_checkbox;
    }
  }
}

================================
In After Lightbox Display:

//Auto-check opt-in checkbox
var iframe = document.getElementById(“lightbox-iframe-” + lbid);
  if (iframe !== null) {
    var iframeDocument = iframe.contentDocument || iframe.contentWindow.document;
    if (iframeDocument) {
      var iframeOptIn = iframeDocument.getElementById(‘form_input_opt_in’);
      if (iframeOptIn) {
        iframeOptIn.checked = PRIMER_CUSTOM_JS_GLOBAL.precheck_checkbox;
      }
    }
  }