Transmit can preview an HTML file in your web browser if you are connected to a properly configured favorite.
For this feature to work you must be connected to a favorite. The favorite's configuration must include the "Root URL" and "Remote Path" fields. The Root URL must be set to the equivalent URL for the Remote Path. For example, a site with the root URL http://example.com/ might be rooted at the path /usr/local/apache/htdocs/example/. Ask your web hosting provider for help if you don't know this information.To preview the selected HTML file in your default web browser, choose File > Preview in Browser