Thanks, W3. I know this sentence is wrong, but I don't think "for ten days" is particularly wrong, although it might sound a bit more formal than "ten days". The point I find weird in the sentence is that it uses the present perfect in combination with "in August 2004", a time adverbial which indicates a specific past time and therefore should be used in combination with the simple past. In fact, the sentence was written by a French person and probably he translated word-word wise into English what he expressed in his language ("J'ai séjourné pendant dix jours dans Coco Palm en august 2004 pour notre lune de miel"). The French phrase "J'ai séjourné" corresponds to "I stayed", not to "I've stayed".
paco