I started with the same approach as MurrayEaton, but realized that may not quite meet the goal of “pushing down footer to accommodate” the page content height, as it places the footer over the content (if the content is longer than the browser window) rather than keeping it at the bottom of the content.
Here is a demonstration of both approaches, (1) a fixed header, footer and sidebar (aka, “floating”, or “pinned to browser” in Axure lingo) and (2) a footer in a page master that automatically moves to the bottom of the content, and sidebar that resizes to height of content.
https://qvzjch.axshare.com
MasterHeaderFooterSidebar.rp (278.2 KB)
The master, “Page Master Pinned” works similar to MurrayEaton’s solution, but any body content can be used anywhere on the page, and the size of the header, footer, and sidebar can be changed in the master without needing to change the master code. Page 2 and Page 3 use this same master with different content.
The master, “Page Master 2” uses the second approach, keeping the footer at the bottom of the content without pinning it to the browser window. In order to accomplish this, all page body content must be placed inside the “Content Panel” dynamic panel. In order to allow the content to be different on different pages, the master must have a drop behavior of “Break Away” --meaning that as soon as it is dragged onto a page, it is dissociated from the master. Any later changes to the master would not affect that page. In effect, a “break away” master is just like a library widget and not a true master. I purposely made the master short to show that “longer” content could be created and it would adjust automatically on page load. (Although this can make editing a little ugly.) Also, see Page 5 which has a repeater list to demonstrate that dynamic changes to the page content height are nicely handled.
So, this solution is not complete, but was the best I could figure out in Axure. Someone else may have a better solution.