Why is this JSTL giving this error?

[Steven]

This code :

---

<c:set var="rssTitle" scope="page">
<rss:itemTitle feedId="example1" index="1"/>
</c:set>

---
Gives this error :
description The server encountered an internal error () that prevented it
from fulfilling this request.
javax.servlet.ServletException: javax/servlet/jsp/el/VariableResolver


While this code works :

 

[Andrea Desole]

This code :

---

<c:set var="rssTitle" scope="page">
<rss:itemTitle feedId="example1" index="1"/>
</c:set>

---
Gives this error :
description The server encountered an internal error () that prevented it
from fulfilling this request.
javax.servlet.ServletException: javax/servlet/jsp/el/VariableResolver

the type of exception just says that there is something wrong with
resolving a variable, but the set tag looks fine. I can't tell the same
about the rss tag, because I don't know it.

While this code works :

well, this other code looks completely different, so it doesn't really
help. Try something like

<c:set var="rssTitle" scope="page">
test
</c:set>

and if it doesn't work, try some other variable names and scopes.