IWP is no longer possible in FileMaker 13. You'd need to use WebDirect from FileMaker Server. This is a major change on FileMaker's part that will profoundly affect people who previously did a "small scale" IWP from FileMaker Pro or FileMaker Advanced.
Bummer. They must have realized there were major security issues that they could only solve through FileMaker Server.
Looking at the feature set, it would seem that WebDirect much more faithfully produces a full "FileMaker Client" like user interface in a Web Browser and I suspect that this could not have been produced from FileMaker--plus I would guess that they wanted a better return on their development investment.
This is just a guess on my part.