let it work under ff 3.5 Rated 5 out of 5 stars
1. download the installer from http://crypto.stanford.edu/PwdHash/#download with rightclick "save target as" on your desktop.
2. change the extension from xpi to zip. confirm the warning
3. open with winzip or winrar
4. open the the folder install.rdf with wordpad and search for:3.0.*
5. change from 3.0. to eg 3.6 and save it.
6. delete complete folder "META-INF" in the zip folder.
7. Close the zip archive
8. rename the zip archive back to xpi. confirm the warning.
9. open the xpi via ff, or doubleclick and>>> evrything works.
excuse my bad english. greetings from thee deep west south of germany