Your banner image is most likely contained within a page wrapper, locate the page wrapper that is being used for the page and follow the steps below:
  1. In the list of page wrappers, to the right of the page wrapper name, choose "Manage Versions"
  2. Look for the version with the green status of "Active" this is your current page wrapper
  3. Click "copy" next to the active page wrapper (We will use the copy as a way of protecting the live page wrapper)
  4. Once you have copied the page wrapper, click "edit" next to the version you just created
  5. Go to step 4 "HTML Body"
  6. Make sure you are viewing the HTML Body in the WYSIWYG editor, rather than the plain text editor
  7. When you see your banner image in the WYSIWYG editor click on it, and then click on the tree icon in the tool bar
  8. A window will open that will contain information on the image including the width and height.
  9. This width and height will need to be the size of your replacement image.