Mathml Rendering Problem

Hi all,

I am new in the group, may be this is naive question, I tried the IRC
#mathml no one is answering there.

Here is the problem I am having:
from the test suit I got
http://www.w3.org/Math/testsuite/mml2-testsuite/index.html the expression
for "not a subset" symbol as the following. But my firefox 10.0.1 is unable
to render it ., here is the fragment

<math>
      <apply>
        <notsubset/>
        <ci> A </ci>
        <ci> B </ci>
      </apply>
    </math>

in the test page it is rendered correctly but whenever I am trying it
offline in a html page then it is showing A B,
Is there a plug in needed or I am doing a dumb mistake.

Please help...

-- 
Hirak Sarkar