A High Rankings thread named How Do Search Engines Treat Punctuation? discusses a common problem people have when trying to optimize for keyword phrases that are searched on 50% of the time with a punctuation and 50% of the time without it.
In the example in the thread, we have these two keyword phrase combinations.
You can see how the results differ. Normally punctuation is treated as a space by a search engine. So how do you optimize for both phrases on one page? Most people do not want to use the phrase improperly, because it looks like you don't know how to spell. But one thing you can do it get links to your page with both types of phrases. This way the people linking to you look bad, and you don't.
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