How can a developer customize the look and feel of a Liferay site?

Customizing the look and feel of a Liferay site is effectively achieved by employing Liferay Themes and layouts. Themes allow developers to change the appearance of the entire site, including colors, styles, and even the layout of page components. By creating or modifying themes, developers can harness the full potential of Liferay's front-end capabilities, ensuring that the design aligns with the brand or requirements of the project.

Layouts play a crucial role as well, enabling developers to dictate how content is presented on different pages. This includes setting up custom portlet layouts and views that cater specifically to the needs of the end-users.

The other methods mentioned, such as modifying the database structure, do not pertain to visual customization and could potentially lead to system instability or performance issues. Using third-party libraries might enhance certain functionalities or styles but does not provide the cohesive site-wide look that themes and layouts accomplish seamlessly. Additionally, changing server configuration primarily impacts backend behaviors and performance rather than the actual content presentation experienced by users. Thus, themes and layouts are the dedicated tools within Liferay for customizing the visual aspects of a site effectively.