It seems like you have opened this file by double-clicking on it. In order to test your build in a browser you need to load this file from a web server. You can either upload this file and the rest of the files from a Defold HTML5 bundle to a web hosting service OR host them using a local web server on your home network.
There is one game object containing the background sprite. It is set at Z position 0. The bunny is another game object containing a sprite. The bunny game object is at Z position 1.
If you want to play with these examples, you can get the project on Github.
Do you want to see more examples? Why not write a few yourself and submit a pull request? We love contributions.GITHUB