Final answer:
The default page of a browser when it's opened is called the home page or start page. The setting of default pages has been significant in antitrust cases, like Microsoft's bundling of Internet Explorer with Windows, which cornered the market and led to legal challenges.
Step-by-step explanation:
The common term for the default page that appears when a browser is initially opened is known as the home page or start page. This page can be set to a specific website by the user or can be the default website provided by the browser. The practice of setting a default home page has historical significance in the tech industry, as seen with the Microsoft Corporation including Internet Explorer with its Windows operating system.
This move led to antitrust litigation because it was viewed as giving unfair competition to other browsers like Netscape Navigator, particularly as Microsoft had a dominant market share. Over time, the control over default settings in software continues to be an important aspect of market competition.