This website is based on the 1928 Book of Common Prayer. However, there's a catch to that statement. Some of the 1928 BCP was changed after the year 1928 - yet there was no change to the date of the book itself.

What was it that changed? The Lectionary. The Lectionary is the term commonly used to denote the tables which set forth the Psalms, Lessons, and the selection of Propers (Collect/Epistle/Gospel). There was a great deal of disapproval with the original 1928 Lectionary, which was very limited in scope with its usage of the Psalter, and also did not try to coordinate the Lessons at Sunday Morning/Evening Prayer with those at Holy Communion. Work was soon initiated on an update to the Lectionary, which was completed in 1940. The changes were adopted by the General Convention of 1943, and thereafter became the official Lectionary for the BCP.

So - since the date of the BCP didn't change, how can you tell if you have a 1928 BCP with the original Lectionary, or one with the 1943 Lectionary? The first thing to do is check the date of printing; if it is after 1943, it should have the 1943 Lectionary. If there's any doubt, or you cannot find a printing date, there's another easy way to check. The page usually on the reverse of the title page includes a statement that reads something like "....conforms to the Standard Book of Common Prayer as adopted by the General Convention...."