"Suffering eyestrain from looking at a flickering monitor? Can't
quite fit everything you want in your display? Ordinarily, problems
like these call for a new monitor, or at least switching to a
different standard resolution--say, going down in resolution if the
problem is flicker, or going up from 1024x768 to 1280x1024 to get
more screen real estate.
"Linux, though, is about extreme configurability and choices,
and it (or XFree86, really) provides you with tools you need to
tweak your video modes to make the best use of your monitor. To be
sure, the procedures described here won't let you make huge
differences in your display, but they will help you get the most
out of your video card and monitor by increasing the refresh rate a
bit, squeezing a few extra pixels onto the screen, or both..."