Insert Google Analitics code to Prestashop

Be carefull. You should not have any strings in your smarty template like this:
"{x.."
, because it's reserved for smarty variable and Prestashop uses smarty templates Instead use this:
"{ x...".
F.g:
<script>
  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','//www.google-analytics.com/analytics.js','ga');

  ga('create', 'UA-....', 'auto');
  ga('send', 'pageview');
</script>
->
<script>
  (function(i,s,o,g,r,a,m){ i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
  })(window,document,'script','//www.google-analytics.com/analytics.js','ga');

  ga('create', 'UA-....', 'auto');
  ga('send', 'pageview');
</script>