This CSS code styles a webpage with a white background, a container with a maximum width of 600px, a box-shadow effect, and padding. It also centers headings and has styles for messages and links. The code also includes styles for input fields and buttons, including a hover effect for buttons. The container also has a "Go back" button styled, which gets bigger on hovering. The button-container is designed to live within the container and is displayed as a flex element.