Hello caroleriva, and thank you for your question.
When you click on the HTML source button in the TinyMCE editor in Joomla, are you still seeing your <script> tags there, or have they been stripped out?
If you followed the steps in our how to add an iframe to a Joomla 2.5 article, you should have removed the word script from the Prohibited Elements section. You might also need to make sure your Super Users are set to have no filtering by going to Site > Global Configuration > Text Filters in the admin panel.
It looks like Joomla automatically updates it to this after being saved:
Thank you for the reply, i can't see the pop-up message in my browser after adding the code you said, however my js code is now working without making any changes.. looks strange, but it works :))