Ed,
Those ‘squares’ are really the character called ⇒ (double lined right arrow) and are displayed if your browser uses iso-8859-1 as it’s character set. I snapped your forecast on my Firefox browser (which has View Character Encoding as Auto) and it displays correctly.
Now that you have the script running, you can customize the output display using CSS styling for class=“WXSIMforecast” – the download page (Saratoga-Weather.org - Scripts - WXSIM display utility ) has examples of how to include it in your pages and other configuration options.