If you don't include misspelled words, and a potential visitor/customer types in a misspelled word into a search engine, how would they ever get to your site? As long as people are not perfect spellers, I think you're going to need to include commonly misspelled/misspelt words. Hopefully the search engines won't penalize you for doing that. If you don't want to put them in your visible text (and look like a dolt), about the only other place would be the meta keywords. Remember that some search engines (e.g., Google) don't place much weight on meta keywords, due to past abuse by page designers. alt= entries might be another place to use them "more naturally". If certain (commonly misspelled) words are so critical to getting visitors to your site that you can't do without them, you might put a small text paragraph down in the footer labeled "Keywords" and include both correct and incorrect spellings there. I would not use hidden text (e.g., white-on-white) as that's considered black hat SEO and could get you penalized.