How do you keep sane in web-app development? Rather what is the normal workflow for making UI in web-apps? How do you keep the abstractions from leaking over?

How do you keep sane in web-app development? Rather what is the normal workflow for making UI in web-apps? How do you keep the abstractions from leaking over? It seems you need to keep all the CSS quirks in your head to be productive. As a counterpoint in something like WPF, I do not need to know much or anything about XAML to produce a usable UI quickly that will not break in bizarre ways. Same goes for PyQT, a few hours starting from scratch(ie not knowing anything about PyQT) and you can make something usable. WxPython same thing, classes in a control such as wx.dataview look normal enough.