I’m not sure from your description what you want to achieve but
<div id="pags"><a href="http://www.anotherserver.com/userfolder/formulario.php"></a></div>
is certainly not going to load anything into a frame. This is simply a link without a description. Take a look at the source of the page where you placed {{pags}} and see if you can spot the above markup. I bet it’s there (that is if ’pags’ is a chunk indeed). It’s simply not showing anything because there’s nothing visible to show.
Try:
<div id="pags"><a href="http://www.anotherserver.com/userfolder/formulario.php">Go there</a></div>
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If you want to load an external script into a page you need to use a snippet and write some php to include the external script. However it depends on what the external script was designed for if you get any sensible output or not.
if you create a new snippet with code something like this you should be able to include an external script.
<?php
if( isset($script) && file_exists($script) ) {
return include($script);
} else return "Script could not be found";
?>
You would insert this into your page with something like this:
[!snippetName? &script=`/path/to/external/script.php`!]
This is a very simple example and there are better ways of including php into your page but without knowing what your external script looks like this is the easiest I can offer.