I'm going to ask a dumb question as someone who is just learning node. What's wrong with serving assets out of public/ in an Express app? Why would someone not want to do this?
For the vast majority of sites that ever hit the web, yeah, it will probably be fine. So go ahead and have fun learning node and do it however, you can always fix it later if the site gets overloaded.
At some volume though, you want to do what the grandparent recommends -- front your application server with nginx, apache, or something. Otherwise serving up static assets is taking away resources that should be spent on the application. Consider if you have a page with 5 images, 5 JS files and 5 CS files for each page created. That means you're serving 15 static assets for every 1 dynamic asset you'd really want to use Node for. While Node can still be "good enough", it is not spending its time doing the stuff you really want to use it for in the first place. A dedicated piece like nginx goes much further.
