My X11 setup contains some truly ugly fonts. In particular, it contains bitmap variants (unaliased, of course) of some common fonts, donated by Adobe. That must have been swell in the nineties but it isn’t anymore. But they’re still included in X.org X11, spreading uglyness when referenced explicitly:

This very much isn’t how I like my webpages. In this case, drilling down to the font declaration (use the excellent Firebug if you have to) yields:
BODY { font-family: "new century schoolbook", times, serif} H1 { font-family: "new century schoolbook", times, serif}
Is this ‘new century schoolbook’ font one of those Adobe bitmap fonts? ‘xlsfonts’ yields:
$xlsfonts | grep -i century -adobe-new century schoolbook-bold-i-normal--0-0-100-100-p-0-iso10646-1 -adobe-new century schoolbook-bold-i-normal--0-0-100-100-p-0-iso10646-1 -adobe-new century schoolbook-bold-i-normal--0-0-100-100-p-0-iso8859-1 -adobe-new century schoolbook-bold-i-normal--0-0-100-100-p-0-iso8859-1
[... dozens more]
So, let’s get our font subsystem to remap this font declaration to something more appealing. You’ll need to edit your fontconfig configuration which is described rather exhaustively elsewhere and add a stanza like this one:
<match target="pattern" > <test name="family" qual="any" > <string>new century schoolbook</string> </test>target="font"> <edit mode="assign" name="family" > <string>Nimbus Roman No9 L</string> </edit> </match>
This is, of course, particular to my wishes and the fonts available on my system. Run fc-cache, reload the webpage with the offending font, and tadaaaa:

Much better.
Update @20091208: With Gentoo, you can use the eselect system to accomplish this. Run eselect fontconfig list and pick the number corresponding with 70-no-bitmaps.conf. Enable it with eselect fontconfig enable $thenumber.
From the 70-no-bitmaps.conf file, it appears there’s a much better way of handling this:
<fontconfig> <!-- Reject bitmap fonts --> <selectfont> <rejectfont> <pattern> <patelt name="scalable"><bool>false</bool></patelt> </pattern> </rejectfont> </selectfont> </fontconfig>
Tags: en_GB, fontconfig —

