It sounds like you are running into a browser caching issue. I find that whether I am working locally or on a live mango server I have to explicitly have the browser not cache files when I am previewing changes.
If you are using google chrome you can have you developer tools open and check the box that says 'Disable Cache' under the network tab. Now when you refresh the page with the dev tools open it will load a fresh copy of all source files.
If you are using Safari I find that you can do a cmd+opt+e to clear cache before hitting cmd+r to reload the page and it will do the same.