Clicking Go should open up your default web browser and show you a
site, slowed down.

On your machine it looks as if your html editor has become the default
application for these kinds of things.

There are two things you can do:

1) Find a way to prevent your html editor from being the default
application. Not sure exactly how to do that.  One way might be to
find a .htm or .html file, right click on it, select Properties and in
the window that appears press the "Change..." button next to the
"Opens with" message.  You should see your web browser listed in
Recommended Programs. Select it, make sure "Always us the selected
program to open this kind of file" is checked and click OK.  Then
start Sloppy and give the Go button another test.

2) Otherwise, if you're just curious to see what Sloppy does, once
you've hit the Go button and your editor has opened :-( just start
your web browser and go to http://127.0.0.1:7569

Option two is simulating what the go button is trying to do, which is
just open your default web browser on the page http://127.0.0.1:7569