Version:           4.0 (using KDE 3.1.3)
Installed from:     (testing/unstable)
Compiler:          gcc version 3.3.1 20030722 (Debian prerelease)
OS:          Linux (i686) release 2.4.20-1-k7

Although rendering of an html page has flexibility on width - konqueror is seemingly choosing a width that is slightly wider than the available area and causing the window to have a horizontal scroll bar.

It is almost as though the width of the vertical scroll bar has not been subtracted from the window size.  A simple test seems to bear that out - if select a page with only a small amount of text (for example the text that apache sends when there is a request for a page that is not there) I can vary the window width and never get a scroll bar.  If on the other hand I use a longer page - regardless of window width I always have a horizontal bar with a small amount of movement (unless the page is genuinely wider than the window - in which case the horizontal scroll bar gives more movement).