Not Work Rated 1 out of 5 stars

Not work anymore..

No longer works Rated 1 out of 5 stars

Unfortunately no longer works with current Firefox versions as of August 2016. There's a bug open on the GitHub page since Dec 2015 with no response from the developer, so looks like this is add-on is abandoned now.

Rated 5 out of 5 stars

Extension works great. F9 will load in the updated CSS without reloading the page. Great for working on pages with lots of JavaScript/interaction type layouts.