Using JS within a page

Hi

I’ve been embedding a .js link for a third party plugin in the text editor of a page. It looks something like this:

<!--Javascript Begins-->
	<div id="ff_container">
	<SCRIPT LANGUAGE="JavaScript" type="text/javascript" src="https://www.myexampleplugin/plugin.js"></script>
	</div>
	<!--Javascript Ends-->

It was working fine when I signed the site off a few weeks ago, but now nothing is appearing on the page and when I re-enter the code and save, everything between the “ff_container” div disappears.

Can anyone help with this please?

Thank you