Blood Type Compatibility. Your ABO blood type is based on the presence or absence of the A and B antigens on your red blood cells. The A blood type has only the A antigen and the B blood type has only the B antigen. The AB blood type has both A and B antigens, and the O blood type has neither A nor B antigen.
Green Triangle. The green triangle appears in the upper left hand corner of a cell when there is an error in a formula. Sometimes Excel will report an error when you use text in a box and the program believes it is part of a formula. When you click on the green triangle there will be a yellow box that looks like a road sign with an exclamation point in it. This button is the Trace Error option that will help you correct your formula.
It means that the row or column which comes after the dollar sign is anchored or absolute. When you copy Excel formulas, they will copy cells referred in that formula relative to the position where they are being copied to. Let's take a simple example. In Cell A1, I have the value 10. In Cell B1, I have the formula +A1. Cell B1 displays the value of 10 (since 10 appears in Cell A1).