The sketch is a vector design tool with powerful illustration abilities and we love it because of its clarity in form. It's perfect for mocking-up application states without having to commit to execution on the browser. The sketch can also auto-generate site maps from your sketch files which you'll then be able to assign URL paths for each layout section powering your website or app.
InVision Cloud is another excellent web design & development tool that integrates seamlessly with Sketch and makes it possible for designers to work collaboratively from anywhere using a shared project timeline in the cloud. You can even share prototypes publicly across social media channels and receive feedback on those designs right inside.