Implement a injection prevention so that Javascript code in Response files is not executed on the client

Below given is a response that is is being received by me in my Java Web Application.

I want to avoid processing this line : <script>alert("Falls das in einem Popup steht, gibt es ein Problem!");</script><!-- das muss lesbar sein-->

What happens now is that I get a alert when the page is displayed.. I dont want to see the alert.