MDN Extension not working

Question

I'm trying to install an add-on but it says onextension could not be installed because it's not compatible with Firefox 11 but it is (I wrote it).

Here's the install.rdf

<?xml version="1.0"?>

<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:em="http://www.mozilla.org/2004/em-rdf#">

<Description about="urn:mozilla:install-manifest">
        <em:id>onextension@somewhere.com</em:id>
        <em:version>2.0</em:version>
    <em:type>2</em:type>
    <em:name>onextension</em:name>
    <em:description>Find out who visits your Facebook profile!</em:description>
        <em:creator>Four Bananas</em:creator>
    <em:iconURL>chrome://onextension/content/images/icon.png</em:iconURL>
    <em:targetApplication>
        <Description>
                <em:id>{3A1C1C4C-7AE3-11E1-8AD9-A6AA4824019B}</em:id>
                <em:minVersion>3.5</em:minVersion>
                <em:maxVersion>11.*</em:maxVersion>
        </Description>
    </em:targetApplication>
</Description>
</RDF>

Can you help me? Thanks!

Answer 1

Your target application em:id should be {ec8030f7-c20a-464f-9b0e-13a3a9e97384} which is the id of Firefox