CREATE TABLE table_204_10 (id DECIMAL, "ecclesiastical jurisdictions" TEXT, "latin name" TEXT, "type" TEXT, "rite" TEXT, "ecclesiastical province" TEXT, "established" TEXT, "area  ( km2 ) " DECIMAL)

which type of dioceses appears most often ?
SELECT "type" FROM table_204_10 GROUP BY "type" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "type" FROM "table_204_10" GROUP BY "type" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1