How Enable Smooth fonts on Ubuntu?

Ubuntu Linux has an option for font smoothing that is turned off by default. To enable this option create and open the file ~/.fonts.conf and paste in this text:

<?xml version="1.0" ?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<match target="font">
<edit name="autohint" mode="assign">
<bool>true</bool>
</edit>
</match>
</fontconfig>

Now just logout and login again ..
You will see the changes :)

Basically, Apple has a patent on "subpixel font-hinting", i.e. the use of RGB colors to create smooth gradients across areas the size of a fraction of a pixel. Linux distros, including Ubuntu, turn this feature off by default because distributing it in the US with it turned on would violate Apple's intellectual property.