Hi Leon,
Please see here -
http://murga-linux.com/puppy/viewtopic.php?p=539413
Specifically, the very last post in that thread where the user edited an entry
via about
:config
In other words, where you normally type the URL, type about
:config then press enter.
Then right click on general.useragent.extra.seamonkey and change its value to
"Firefox" as suggested. Restart the browser.