In Ashkenazi siddurs God's name is spelled with two yuds; in Sephardi siddurs we find them spelled as YKVK with the word a-d-o-n-o-y placed inside the last "hey". Also, on occasion, God's name (YKVK) gets three extra vavs.
Is there a reason for this type of printing of God's name in Sefardi siddurs?
I am sure it has something to do with Kabbalah.