Question: I inserted a Google Tag Manager code snippet below the body tag but my website will only display a blank white page. When I remove it, the page displays correctly.

```
<!-- Google Tag Manager -->
<noscript>
<iframe src="//www.googletagmanager.com/ns.html?id=GTM-XXXXXX" height="0" width="0" style="display:none;visibility:hidden">
</iframe>
</ noscript> 
<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start': new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0], j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src= '//www.googletagmanager.com/gtm.js?id='+i +dl;f.parentNode.insertBefore(j,f); })(window,document,'script','dataLayer','GTM-XXXXXX');
</script> 
<!-- End Google Tag Manager -->

```

Answer: 
Just spend half a day on it. If you have the same problem has me it is because you are using Smarty and he doesn't recognise it as Js or something like that.
I had to use `{literal} ... {/literal}` tags. 
Hope this could help someone.
I found the solution of these.

They change something in the URL

In the blank frame <https://www.googletagmanager.com/>**ns.html?id=G**TM-XXXXXXX"

and the Iframe who really works is with these

<https://www.googletagmanager.com/>\*\*gtm.js?id=\*\*GTM-XXXXXXX 

Let me know if they work for you