Firefox addon devellopment - getting addon not compatible error message

I am building a firefox addon for the first time. When I try to install I keep getting this error message "Addon not compatible with firefox 4.0"

I tried to install on older version of firefox also but no luck. I am not sure what i am doing wrong. Here is my install.rdf file.

<Description about="urn:mozilla:install-manifest">
    <em:id>priyank@techstudio.in</em:id>
    <em:name>Chrome Dictionary</em:name>
    <em:version>0.1</em:version>
    <em:type>2</em:type>
    <e开发者_Python百科m:creator>Priyank Gandhi</em:creator>
    <em:description>A sample extension.</em:description>
    <em:homepageURL>http://www.priyankgandhi.com/</em:homepageURL>

    <!-- Mozilla Firefox -->
    <em:targetApplication>
        <Description>
            <em:id>{ac236786-4ca7-48d0-8f3b-034fe9ad2dbc}</em:id>
            <em:minVersion>3.0</em:minVersion>
            <em:maxVersion>6.0.*</em:maxVersion>
        </Description>
    </em:targetApplication>
</Description>

Here is the structure of my files:

|-chrome.manifest
|-install.rdf
|-chrome
|mydir
||content
||-main.xul
||-main.js
||skin
||-main.css

Thanks

I think your target application em:id is off:

{ec8030f7-c20a-464f-9b0e-13a3a9e97384} - Firefox's application ID.

Source: https://developer.mozilla.org/en/Building_an_Extension