When I upgraded my Firefox to the (then) latest version v33.0 I lost my spell check feature in the browser, those tiny zigzag(?) red lines below your misspelled words.
I didn’t consider looking for a solution thinking the next update would have it fixed. Then came the version 34.0 which apparently arrived very fast. But this hadn’t fixed the problem either.
Finally I decided to ‘Google’.
Then found out that it was rather a simple fix.. Which didn’t require a RESTART! The happiness on a Firefox user’s face when they don’t have to restart their browser for an Addon is priceless. XD
Back to the fix.
Here is how to fix your Spell Check feature on Firefox.
Step 1. Find out which language your browser is using. (English, French, Chinese)
Step 2. Open the following link and locate your language from the list. [Firefox Dictionaries & Language Packs]
Step 3. Click on the Install Dictionary button next to the language.
Step 4. On the new page, Click on Add to Firefox button. Just like you install any other extension.
That is it. Now just refresh the page where you want to type and misspell a word. Those red lines should appear now.