I believe that this is a known limitation of FileMaker when using IWP. There is a pricey (or so others have complained) add on from a third party: SuperContainer that provides a work around.
Thank you for your post.
The answer provided by "PhilModJunk" is correct. (Thank you!).
Pull down the Scripts menu and select "Manage Scripts...". Double-click any script (or click the "New" icon in the bottom left corner) to edit the script. In the "Edit Script" dialog box, you will see all the available script steps listed on the left side. At the bottom of that list is a pop-up for "Show Compatibility". Change the pop-up to "Web Publishing", and all steps that unsupported are grayed out (including "Insert Picture" and "Insert File").
In your case, the buttons are probably set up to run scripts with these commands. This should help you in the future if you create scripts for Instant Web Publishing.
Let me know if you need additional clarification.