Cache and content_for

Hi!

I want to cache some fragment to place in a sidebar of my default layout,
and i want to use content_for to place it.

It the API it says:

NOTE: Beware that content_for is ignored in caches. So you
     shouldn't use it for elements that are going to be fragment cached.

I am not really sure what means, because i have tried placing a cache block
inside a content_for block and it looks that it works.

I want to know if i am using it correctly and wether it will be a problem in
the future because that's not supposed to work.

In my general layout i have:

/app/views/layout/general.html.erb :

...
   <div id="divsidebar">
                          <%= yield :sidebar %>
   </div>
...

In mi view, i have:

/app/views/controller/index.html.erb :

...
<% content_for :sidebar do %>
<% cache(:action_suffix => "tagcloudcache") do %>
  ...
  <%= render(:partial => "tagcloud") %>

<% end %>
<% end %>
...

My question is:
Is that not supposed to work? Because it works. Is there a better way of
doing it?

Thanks a lot for your attention!!

-- M