There are two Typo Instincts.
On the one hand: Who cares about a single typo? If someone can’t spell (or run spellcheck), does that really mean they can’t do their job?
On the other hand: Who wants to work with someone who can’t even bother double-checking their first impressions?
I don’t know for sure if typos ruin online sales pitches, but I have a theory, and I’m going to test it.