I'll give you the preview thing. A noob probably wouldn't know how to fix html. On the other hand the internet gets to be part of our daily lives more and more. Kids are learning computers in school now, so a general sort of computer and internet literacy becomes part of common knowledge.

And, knowing nothing about the technical background of the site, just from the way it works, it seems to me that preview and spell check go together. You'll get a preview with each spell check though you can have preview without spell check. Then it comes down to the decision of does the site just provide the spell check button and hide the preview button somehow or does it provided two buttons (or button/checkbox combination) and trusts it's users to make one more choice. For a second I was thinking about a combined preview/spell check button, but that be really hard to do, because you'd need a spell check that can recognize all the different alphabet and languages in the world and that might just be a tad difficult and resource hogging.