iWebMore could be considered as a plugin that adds an extra feature to iWeb. If you've stuck with Apple's web editor instead of flocking off to more elaborate alternatives you've surely been frustrated with some limitations in iWeb.
iWebMore makes pasting HTML into Apple's web editor accessible to anyone. All you have to do is select the publish folder, paste your HTML and press generate.
iWebMore does not support plugin code and you'll need to make sure you've prepared iWeb to receive the HTML text (by inserting a rounded box from the Shapes tool in iWeb).