1 Click on the new topic button.

2. Type something inside the content.

3. Click on spell check button (ABC with check mark).

Error message: There was an error processing the request.

I think you are right, Don't know about Maxthon or Safari. They are installed on my system. But I never use those browsers.

Now all the old browsers like IE 8 and down doesn't have spell checkers, So this is where yaf spell checker comes into play.

You need to update to the newer nightly build, looks like you are using an older version

All modern browser have it, this was an option for older ones.