accompanying.html

<div id="form_submit">
<input type="image" title="submit" src="/images/icons/submit.png" name="submit" id="submit" class="forward"/>
</div>

yui3_insertHTML.js

// currently undocumented, but presumably very handy method in YUI3

var GLOBAL = {

signupSwitchForward : function () {
  
  signupSwitchForward: function() {
    YUI().use("node", function(Y) {
      Y.get('#sign_up_two').setStyle('display', 'none');
        if (Y.get("#form_submit").insertHTML) {
          Y.get("#form_submit").insertHTML('<a class="forward" href="#sign_up_one">Next step</a> <a class="back" href="#sign_up_one">Back</a>');
        }
        else {
          Y.log("I can't find that method on the object");
        }

        if (Y.get('#submit')) {
          Y.get('#submit').setStyle('display', 'none');          
        }
        else {
          Y.log("It ain't in the dom, bucko");
        }

      });
   }}