Exceptions are errors or unintended program behaviors that occur while a program is running. Exceptions indicate that a script needs to be "debugged" or fixed.
If you have noticed exceptions while your program is running, you will want to view information regarding the exception in order to fix the script. To do this, create a file named web.config (or edit an existing one) and place the following code in it to view complete exception information. Please note that this will display full exception information publicly and should only be enabled for short times while debugging.