I try to use frameworks which contain building blocks, so I can just use existing functional elements (like Alert in Bootstrap, etc.) without having to come up

I try to use frameworks which contain building blocks, so I can just use existing functional elements (like Alert in Bootstrap, etc.) without having to come up with my own css rules. Obviously, this works only if you don't need any custom elements, but I'm not a designer, so I just usually use what's available.