In addition to the comments given from all the above respondents, I would also like to point out that, though for nowadays the term "merci pour [+objet direct]" (equivalente a "gracias por [+objeto directo]" en español) is more widely used, this term is traditionally known as "merci de" instead. In particular, if the described matter is an infinitival phrase, then one has to use the term "merci de..." For instance,
merci d'être venu(e) = thank you for coming
merci d'avoir appelé ..(le nom de compagnie) = thank you for calling ..(the name of company) -- This happens if you call some company where they provide you a tape recording, asking you for instructions.
Meanwhile, the difference between "votre" and "ton/ta" ("vos" and "tes" for plural nouns) given from above is basically same as the situation of "su" and "tu" ("sus" and "tus" for plural nouns) in Spanish respectively, i.e., it depends on whether the speaker addresses the other party as "Ud."(vous) or "tú"(tu).
P.S. You may also refer to the following weblinks regarding the forum discussions on the differences of "merci pour" and "merci de" in wordreference: