We built NationBuilder so users with very limited technical knowledge can be quickly up and running. You do not need to know any HTML or CSS to setup your web site or create new pages. All the best practices for activities such as fundraising, petitions, surveys and so on are built-in, so you take advantage of them automatically.  Facebook and Twitter are also automatically integrated, so you don't even need to figure out widgets. However, if you have HTML and CSS knowledge, you will be able to create custom themes and change everything down to the last detail.