myfaces.apache.org/extensions can't resolve

I did some examples of JSF with tags:

Code:

---

<%@ taglib uri="http://myfaces.apache.org/extensions" prefix="x"%>

---

but it returned to me this exception

javax.servlet.ServletException:absolute uri: http://myfaces.apache.org/extensions can't resolve or in web.xml or in jar files

what is the problem?

this page doesn't exist, and when it tries to search the URI finds an error over there
Change the address to an existing address

You need some jar that contains that you want
and change the http://myfaces.apache.org/extensions route
to the route of this jar