I'm in the exactly opposite (and seemingly rare situation). I started with iOS mobile app development and now would like to move into web apps and not sure wher

I'm in the exactly opposite (and seemingly rare situation). I started with iOS mobile app development and now would like to move into web apps and not sure where to start. I have basic HTML and CSS knowledge. Should I learn javascript properly first (where) or learn about layouts, handling different browsers and things like that. Very sorry for being completely off-topic