Some of the Mac users have mentioned to me some problems getting
a file to properly be an editable .html file that will run
the JavaScript programs when browsed.

I have pulled out my trusty Macbook and tried it with both Safari
and Chrome, and the following procedure should work for you if
you are having these problems.

1) Go to the Examples link on the class homepage; click on Example
and then you are on the Examples page.

2) Click on that first link at the top... the template

3) Your browser whould show the HTML page with the header "Program
template" and showing the run button.

4) Click the "run" button... you should be happy happy happy.

5) Now lets save this webpage as an HTML file on your desktop.
Select the File menu tab for your browser, then Save As and when
the dialog box comes up name the file whatever you want and also
tell it to save as an HTML Only file, or as a Source (not an archive).
Lets say we save it as "temp.html" to the desktop.

6) You should see a file temp.html on the desktop.  Double check it works
by clicking on it and see the browser render the page with the button.
Click the run button and happy happy happy but this time the HTML is
sitting on your desktop, not off on my web server.

7) Lets make changes.  To do this use TextEdit and before you do, open the
Preferences box (go to the TextEdit menu bar tab, select Preferences) and 
then Open and Save... and then check the selection near the top that says 
something like show HTML as text not as rendered information.

8) Now go to the file temp.html on the desktop.  Select Open with 
TextEdit.  You will now see in TextEdit something that looks like what 
you see if you so a show source in the web browser.. that is, you see 
HTML tags, text, and JavaScript.

9) Find the < script ... > tag and under that you will see
  alert("Happy happy happy");
Edit this and make a change, like make it 
  alert("Happy happy happy, Jack!");

Now save the file. Go to your desktop and click on the file to make
the browser open it.  You should see the page with the run button.
Click the run button, and Happy happy happy, Jack!