How will decision making help us when creating websites? In the last chapter we wrote some code that converted temperature in degrees Fahrenheit to centigrade. We obtained the degrees Fahrenheit from the user using the prompt() function. This worked fine if the user entered a valid number, such as 50. If, however, the user entered something invalid for the Fahrenheit temperature, such as the string aaa, we find that our code no longer works as expected. Now, if we had some decision-making capabilities in our program, we could check to see if what the user has entered is valid. If it is, we can do the calculation, and if it isn't, we can tell the user why and ask him to enter a valid number.