Under Linux, if you have Nepali Spell-check enabled for OpenOffice.org (instructions here), Nepali spell-check works in Firefox as well. But for those who want it just for Firefox (or, Thunderbird), I've created a small extension which does the job.
- Download the installation package here or from Firefox Addon Page.
- Drag and drop the file to Firefox and follow the instructions
- For Nepali spell-check, right click in the textbox and select Languages > ne_NP
The extension is currently experimental at Firefox Addon Page. Please drop your valuable review/comments there.