I initially created a Google Plus One button, copied the javascript code, and pasted it into my website. The button was working fine. A few weeks later, the button didn't appear. I tried in multiple browsers, but only blank space showed up where the button is supposed to be. I tried reinstalling, to no avail.
Since I use WordPress for my website, I decided to take the HTML and JavaScript code out and install ShareThis on the homepage and add the Plus One button to it. It doesn't even show up there. You can see it at http://www.wwwbuildawebsite.com/. It is supposed to be between the Facebook Like and Pinterest. However, I see it appearing on another page of my website, http://wwwbuildawebsite.com/tutorials/index.html.
In the rest of my posts, blank space shows up. You can click on any of the links in the Tutorials Page. The sharebar appears at the left; the Google Plus One button is supposed to appear first, before Twitter.
The problem seems to be that you are including mootools-1.2.3 which overwrites the JSON object provided by the browser. The sharethis library fails when trying to call JSON.parse which then fails to render the G+ button.
You could:
1) Upgrade to mootools 2.0 or newer (see https://mootools.lighthouseapp.com/projects/2706-mootools/tickets/741-google-friend-connect-js-api-with-mootools#ticket-741-4)
2) Place your call to asynchronously load plusone.js after you load mootools:
<script type='text/javascript' src='http://www.wwwbuildawebsite.com/wp-content/plugins/superslider/js/mootools-1.2.3-core-yc.js?ver=1.2.3'></script>
<script type="text/javascript">
(function() {
var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
po.src = 'https://apis.google.com/js/plusone.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
})();
</script>
This will re-instate the JSON.parse function after it is overwritten.
3) Manually alias the functions:
JSON.parse = JSON.decode;
JSON.stringify = JSON.encode;