When building websites with scripting languages that require compiling (Sass, Less, Stylus..), compiling them manually (or via refreshing the page) is usually an extra step.
Prepros is an open source application for Windows OS that can do that automatically for Less, Sass, Scss, Stylus, Jade, Coffeescript, Haml and Markdown.
It auto-compiles the source and injects the CSS (also HTML and JS) to the browser so that no refresh is needed.
There are options for the compiling process like the output format or its style (compressed, nested..).
Prepros also has a built-in + static HTTP server for testing any ajax requests.