KDE is one of the best things that have happened to Linux and X in a long time. It provides a consistent user interface that goes a long way towards making Linux accessible to the average non-geek. More information about KDE can be found at http://www.kde.org/. So why am I singing it's praises here? This is because KDE 1.1 has a new feature that will make the fonts and colors in your programs, including non-KDE applications consistent with KDE's current style.
This is very easy. Simply start up the KDE Control Center, go to Desktop, and go to Style inside Desktop. In there, there will be a toggle switch labeled "Apply fonts and colors to non-KDE apps". Turn it on, click OK, and your done! The next time you start up many X applications, they will use the same colors and fonts that your KDE applications do. Some people may like this feature better than others, but if you don't like it you can always turn it off.
Let's face it, Netscape is an important application in Linux. We all use it, and we all need it, so let's look at it specifically for a minute. An out of the box Netscape installation is prone to the font problems we've discussed -- large fonts that get pixelized, splotchy looking fonts, fonts so small they are unreadable. In short, ugly. Maybe this is why you are here?
Hopefully, at this point you have followed the above suggestions. These steps can help greatly. TrueType font availability is almost a necessity, and you need a TrueType font server for this. Many web pages specify font families -- like Arial -- that are not typically available to Linux users. This is bad design, but having some of the basic TrueType fonts available will help greatly in overcoming the short-sightedness of some designers. Microsoft -- can't live with 'em, can't live without 'em.
Assuming you have TrueType working, from the Netscape menu select Edit -> Preferences -> Fonts. Open the Variable Width Font droplist on the right side of the window. Your TrueTypes should be there along with other fonts. Choose which ever one suits your fancy as the default. Check the Allow Scaling checkbox too. If the available point sizes are 0 and 12, you can go down and, and enter your desired point size in the box to the right and click on the OK button. The down-side to this is that Netscape will not remember these settings, and you will have to do this each time you start Netscape. Unless -- you have fonts.alias set up already. Then this will solve these problems. See Section 3.4 for more on fonts.alias.
You might consider experimenting with some ~/.Xdefaults (or perhaps it's~/.Xresources on your system) settings too:
The 'sizeIncrement' controls how much of a jump Netscape makes when different 'basefont' sizes are specified ala:
for instance. The default is '20', which is a pretty good jump. Changing this can help Netscape from scaling to too large and too small of a font. The x and y resolutions are roughly equivalent to 'dpi' settings. Any random number within reason can be used here. Experiment.
$ xrdb -load ~/.Xdefaults
(or .Xresources as the case may be) and restart Netscape. There are many settings that can be tweaked or altered this way. Look at the Netscape.ad (app defaults) file that should be included with Netscape packages.
If this approach does not get the job done as far as the 'tiny fonts' problem in Netscape, then see the fonts.alias section above. You can really fine tune many things with this approach.
Mozilla configuration should be roughly the same. You might find, however, that Mozilla does a better job of handling fonts in X, and pages will look better overall.