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: 
This could be security rules on your firewall. Many web application firewalls will block 0- width frames to block potential code injection vectors.

Try removing the 'style="display:none;visibility:hidden"' attribute and giving your iframe a height and a width of 100.

If that works, then probably some security system somewhere is blocking the iframe, you can normally fix this by moving the iframe styles out to an external stylesheet like this:

```
<noscript>
  <iframe src="//www.googletagmanager.com/ns.html?id=GTM-XXXXXX" class ="gtmIframe">
  </iframe>
</ noscript>...

```

and in your stylesheet:

```
.gtmIframe {
  width:0;
  height:0;
  display:none;
  visibility:hidden;
}

```
Without many details, it is a little hard to figure this out. 

* Is the main code in the head tag?

`<!-- Google Tag Manager -->
<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=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-XXXXXX');</script>
<!-- End Google Tag Manager -->`

This script should be as high in the head tag as possible. 

If this script is present and there is nothing else wrong. Then there would be code around this that is breaking, or code inside of it. Are there tags in GTM setup to do something that may cause the page to break? Is it only this page? Can you create a new page, fresh HTML, nothing else on it except a paragraph and headline, add the GTM code? Once you do this, and assuming the H1 and p are visible, then add the rest of your page, piece by piece, until the page breaks. You will then know what is breaking GTM. 

That is the best advice I can offer without taking a look myself. 

-Cheers