Navigate to the HTML file you wish to open and double-click it to you that file in your browser. Internet Explorer becomes your default browser when you install Windows.

Save your HTML file. Browse to the location of the file on your computer using Windows Explorer. From Explorer you can open the file in a Web browser by double-clicking it.

As a result of this, to preview a file you will need to first set up Safari to open the HTML file on disk, and then when you save changes in TextWrangler you will need to refresh the browser to ...

Type .html at the end of the file name and click on the Save button. This will save your text file in HTML format. Double-click on the saved file and it will open in your default web browser.

Google's latest 'blend online with offline' trick is automatically opening Google Drive files from the web with your desktop apps.