Final answer:
Webmasters control the Main Content of a website, which doesn't include the header, footer, sidebar, and navigation menu, as these are typically part of the site's template. The focus in Main Content is on presenting unique and specific information in a user-friendly manner.
Step-by-step explanation:
Webmasters have direct control over the Main Content of a webpage, which typically excludes elements like the header, footer, sidebar, and navigation menu. These areas are considered part of the site's template or theme, which provides a consistent structure and style across different pages of a website. The Main Content is where the bulk of the website's unique and specific information is presented, such as the text of a blog post, article, or the main presentation of a page. This area is essential for a webmaster when trying to balance text, images, and formatting to ensure the information is easy to digest and engage the website's audience effectively without being overwhelming.