Web page authors can design a web page so that it automatically
adjusts to the width of the visitor's screen. It sounds like your home
page was designed in this manner.
The page width can also be limited. Commonly, the authors choose a
limit that would display best on an 800x600 screen. They do this so
that a page can be viewed on as many systems as possible without
having to scroll left and right. Up and down scrolling only. Visitors
with larger screens, will see extra blank space.