1) There is a dispute among the later authorities (Acharonim) as to whether or not it is permissible for a blind woman to make a blessing over Shabbat candles. According to the Aruch Hashulchan (263:9), since a blind person does not gain real benefit from the light, she shouldn't make a blessing. However, the Magen Avraham (See Mishna Berurah 263:14) permits a blind woman to make the blessing in certain circumstances, such as when she lives alone.

1) The source of this Halacha is the Rema 263:1, in the name of the Maharil. The Eliyah Rabbah writes that a poor woman can add a little extra oil or use a longer candle, rather than having to buy an extra candle each week.

אשה ששכחה פעם אחת להדליק תדליק כל ימיה נר אחד יותר ממה שהיתה רגילה וכן אם שכחה כמה פעמים תדליק תמיד נר אחד יותר והוא משום היכר שתהא זהירה מכאן ולהבא ולכן אם מחמת אונס לא הדליקה אינה צריכה להוסיף

1) In Talmudic times, it was customary to begin Shabbat with ''Bless the Lord Who is blessed'' at the beginning of evening prayers. According to the Mishna Berurah (261:30), nowadays, when the congregation sing the words ''Come O bride'' in the song ''Come my friend to meet the bride'', they are accepting Shabbat upon themselves. 2) There are two reasons for beginning Shabbat early. Firstly, most authorities rule that it is a Mitzvah to begin Shabbat while it is still considered to be ''daytime'' on Friday, i.e., before sunset. This concept is called "Mosif Mechol Al HaKodesh" (adding part of the non-holy to the holy). Secondly, even those authorities who rule that it is not an actual Mitzvah to begin Shabbat early, still rule that everyone should refrain from performing prohibited acts a short time before sunset, because if one got into the habit of waiting until a moment before sunset to begin Shabbat, one could easily end up performing a prohibited act after sunset (see Shulchan Aruch 261 and commentaries). In many communities, the women would wait to light candles until they saw that the evening prayers were beginning in the synagogue; consequently, if evening prayers weren't said early (before sunset), many would end up lighting candles after sunset, thereby desecrating the Shabbat (Aruch HaShulchan 267:4). 3) It is allowed to begin Shabbat anytime after ''Plag HaMincha'' on Friday afternoon, which is always one and a quarter ''Shaot Zemaniot'' (seasonal hours) before sunset. A ''seasonal hour'' is equal to one twelfth of the total time from sunrise to sunset (some say from dawn to dusk) - see the Rema 261:2. 4) Three small stars which are relatively close to each other. 5) There is a dispute in the Talmud as to what is the correct time frame within which one can say the afternoon and evening prayers. Rabbi Yehuda rules that one can only say the afternoon prayers up to ''Plag HaMincha'' (see note 3), and from then onwards, one can say the evening prayers. The Rabbis, however, rule that the time for the afternoon prayers extends until nightfall (in practical terms, this means sunset, because after that point we are not sure when nighttime actually begins), and one can only say the evening prayers after nightfall (that is, from the time we are certain that nighttime has begun, which is when 3 stars appear). Now, it is generally forbidden for those who customarily follow the Rabbis, by waiting until after nightfall to say the evening prayers, to randomly decide to say the evening prayers before nightfall, like the ruling of Rabbi Yehuda. However, since by saying the Shabbat evening prayers before sunset, one is fulfilling the Mitzvah of adding from the non-holy to the holy (see note 2) by accepting Shabbat early, the authorities permitted changing one's custom in this case. However, when following Rabbi Yehuda by saying the evening prayers before sunset, one must be careful to be consistent and follow his ruling regarding the afternoon prayers as well, that is, by saying them before ''Plag HaMincha''. There is an opinion which states that if one is praying with the congregation, one may say the evening prayers before sunset, even if one said the afternoon prayers after ''Plag HaMincha''. However, the Mishna Berurah (267:3) rules that one can only rely on that leniency in pressing circumstances, and only if one waits until after sunset to say the evening prayers (that is, during ''Bein HaShemashot'', the time period in which we are uncertain whether it is ''day'' or ''night'').