Halacha requires that the verses which list the names of Haman’s ten sons should occupy an entire column of the Megila; these names must appear on a separate column, without any other text. It is therefore common to write the names in especially large script, as otherwise, there would be blank space, which, according to some opinions, would disqualify the Megilla (as it would constitute an unwarranted paragraph break).
The Vilna Gaon (Rabbi Eliyahu of Vilna, 1720-1797), however, noted that there is no established tradition that the letters of the names of Haman’s sons should be written in large script. We have such a tradition regarding a number of other letters in the Megilla, such as the "Tav" in "Va’tichtov" and the "Vav" in "Vayezata," but there is no tradition regarding the names of the ten sons of Haman. Therefore, the Gaon maintained that the entire Megila should be written with only eleven lines in every column, so that the column with the names of Haman’s sons will be the same size as all the other columns of the Megilla, and they could be written in normal-sized script.
Most Megillot that are written and used today are not written in accordance with the Gaon’s view. Nevertheless, those who are looking to purchase a Megilla should be aware that there is a Hiddur (means of enhancing the Misva) to have the entire Megilla written with only eleven lines in each column, to satisfy this opinion of the Vilna Gaon.
