If you want to avoid a chunk of deeply unpleasant websites, you could compile a list of their URLs and put them in your computer's hosts file, pointing them to the localhost. This effectively blocks them.
Dan Pollock has done the dirty work for you, so download the pre-configured hosts file and spare your eyes while also improving your computer security for free.
I wish I'd had this the other day, when someone suggested I visit a certain site with Lemon in its name. Which I did while sat on the train. Next to a young woman.