Thomas:
You're right - that does bear some clarification!
Netscape4x has the most bizarre frame boundary calculation that could be
imagined. It calculates ratios of intended frame dimensions factored by
available viewport and rounds fractions down. The result of this is that
there are certain dimensions that simply cannot be achieved. This means
that with a complex (or even moderately simple) background you just cannot
reach a seamless blending from one frame to another in this browser. Look
here to see a graph of the frame dimensions that cannot be achieved -
http://www.jshook.com/netscape_frames/
So - if you are trying to align a horizontal line across a vertical frame
boundary, or a vertical line across a horizontal frame boundary, you will be
OK since it doesn't matter where the boundary is placed. But if your
background image has "horizontal texture" you will see a clear demarkation
across a vertical boundary, and the same for "vertical texture" across a
horizontal boundary. The effect is dramatically exacerbated if you resize
the browser viewport while looking at the alignment (in NN4x).
You can see this on a very old page of mine, at this URI -
http://great-web-sights.com/tutorial/framesizes/Framesizetester.html
Browse there in Netscape4x and resize the viewport to see how large a
disparity you can get between the set dimensions and the actual ones (it
doesn't do anything interesting in contemporary browsers). And whatever you
do, don't look at the code (it's very old, as I said!).
Of course, if you aren't interested in supporting NN4x, then it's strictly
academic.
Does that help?
