Suppose I have changed html file. What is the best way to view results? Am I able to view results right in IDE (WebStorm)? Or I have to open browser by using Alt-F2?
WebStorm doesn't have internal preview, so you need to verify the results in the browser. You can keep it running and just switch to the window and refresh the page, in WebStorm you can enable an option to save files automatically on frame deactivation.
Update: see also the new instant preview feature.