I came across a little trick today to spell check a website you are browsing in Firefox. It’s pretty handy if you have a live site and want to give it a once over without loading up all of your code. To spell check the page just go to it, then paste this in the address bar:
javascript:document.body.contentEditable='true'; document.designMode='on'; void 0
If you add this code as a bookmark on your bookmarks toolbar, then you will be able to spell check a site just by clicking on the bookmark button 
This javascript makes the whole webpage editable, and therefore runs it thought the spellchecker. Nice!
