Sometimes Mozilla Firefox close unexpectedly and restart by itself. Or some plugin made Firefox crazy and crash, usually Adobe Flash. Even you just do browsing, many ads use flash cookies and stored in your Firefox temporary folder. This will make your Firefox slower.
So after that happen, i was looking for a text area cache at Firefox addons website. And i found what i was looking for. You can use Textarea Cache, to save anything you write inside text area or WYSIWYG editor. Every stroke you press will capture and save to a file cache. And if something happen like Firefox crash or Windows BSOD, you still have your backup, and your article is saved.
This plugin help me so much. So if you found a similar problem to my case, then it is worth to try this plugin.