The phrase
default setup is the operative word here, and based on that you are correct.
However, not everyone goes for
default setup - and many people chose to add lots of crazy additions to their browser like:
hotbar
Emoticons,ecards,skins,wallpapers,games - FREE download
ask
sp.ask.com/docs/toolbar/
yahoo
companion.yahoo.com/
google
toolbar.google.com/
ebay
pages.ebay.com/ebay_toolbar/
weather
Weather for New York, NY
sometimes, sites just add them to your setup without even asking - how rude of them! So anyway, having one or more of these
WILL compromise your browser screen size.
That is all.