[totaltec]

No problem.

I think this is because X-cart's Smarty template engine is attempting to parse the {} tags in your JS code. Try wrapping it with {literal}{/literal} tags. Additionally you have used {} to display your script tags, when it should be <>. And finally you have included jQuery, and jQuery is already included in X-cart, and it should only be included once.

So you have not made one, but 3 separate errors! I think you should win a gold star.
Try this code, replacing everything you put after {include file="customer/pop18.html"}:

<script type="text/javascript">
{literal} 
$(document).ready(function(){

  $( ".popup_img_yes" ).click(function() {
    $( ".popup" ).fadeOut( 1200 );
  });
 
  $( ".popup_img_no" ).click(function() {
     window.open("http://www.google.com","_self");
  }); 

}); 
{/literal}
</script>

So you also need to remove this line: {script src='http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js'}{/script}

And I'm not sure about including a .html file like you have here: {include file="customer/pop18.html"}

I would rename that file to pop18.tpl and pull it in with:
{include file="customer/pop18.html"}

But it may be fine, I've never tried to include a .html file before. Leave it that way at first and tell me if it worked!