These are the settings to the File Save operation. Since we are going for a web page,
use jpeg at whatever quality setting you like.

I store the processed images in a directory below the working directory, called "shadow."

SAVE your workflow, then run it.

I do have problems with workflows picking up the wrong masks and applying them. If you
also have this problem, then save the workflow and close the workflow window. Open a new
workflow window and reload the saved workflow, and go through each of the steps in order,
checking their settings. Make sure that when you get to the step where the mask is applied,
that the workflow is grabbing the correct mask. Then run the workflow again.

It usually works for me at this point. I think there's a bug somewhere, and this is my workaround....