statistics → site-statistics
Done. There were only a few questions with each of these tags, and both seem to be used identically.
css → design possibly. If these should not be synonyms, then the tag wiki excerpt for design could use some clarification.
I'll let someone else handle this one, since I don't know enough about website design to even know what CSS means.
wrong-answers → incorrect-answers
Done. These tags are clearly identical.
(And apparently both tags have only ever been used by one user. I get that incorrect but upvoted answers are a pet peeve of his, but it's a pity nobody else has ever seen fit to post to meta about this important site quality issue [unless they have but haven't used the tag].)
edit → editing
Done. The first of these only has a few questions and is clearly synonymous to the second.
interesting-tags → tags: interesting-tags is one of the default tags that the cleanup script won't touch. No one uses it, but it might as well be a synonym of tags.
Nah. I'm not sure what interesting-tags is meant to be for, but if someone comes up with a distinct and sensible meaning for it, they're free to start asking questions with that tag. Let's not synonymise it before it's even been used.
quotes → quotation
Done (ish). I did this merge the other way round, since even though there are more questions tagged quotation than quotes, the latter seems like a more intuitive name for the tag: people ask questions about quotes in questions and answers here, not about famous quotations.