I am using Notepad++ to create a simple web page where a user types in two numbers into a text box, and then presses a button. When they press the button something comes up
Values from inputs are retrieved as strings, you need to convert it to number. Try this:
value1 = +document.First_num.value; value2 = +document.last_num.value;
Also, try to be consistent when naming your input, why caps for one and lowercase for the other?